字符串函数
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str_pad

(PHP 4 >= 4.0.1, PHP 5)

str_pad — 使用另一个字符串填充字符串为指定长度

说明

string str_pad ( string $input , int $pad_length [, string $pad_string = " " [, int $pad_type = STR_PAD_RIGHT ]] )

该函数返回 input 被从左端、右端或者同时两端被填充到制定长度后的结果。如果可选的 pad_string 参数没有被指定，input 将被空格字符填充，否则它将被 pad_string 填充到指定长度。

参数

input

输入字符串。

pad_length

如果 pad_length 的值是负数，小于或者等于输入字符串的长度，不会发生任何填充。

pad_string

Note:

如果填充字符的长度不能被 pad_string 整除，那么 pad_string 可能会被缩短。

pad_type

可选的 pad_type 参数的可能值为 STR_PAD_RIGHT，STR_PAD_LEFT 或 STR_PAD_BOTH。如果没有指定 pad_type，则假定它是 STR_PAD_RIGHT。

返回值

返回填充后的字符串。

范例

Example #1 str_pad() 范例

<?php
$input = "Alien";
echo str_pad($input, 10);                      // 输出 "Alien     "
echo str_pad($input, 10, "-=", STR_PAD_LEFT);  // 输出 "-=-=-Alien"
echo str_pad($input, 10, "_", STR_PAD_BOTH);   // 输出 "__Alien___"
echo str_pad($input, 6 , "___");               // 输出 "Alien_"
?>

字符串函数
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PHP手册 - N: 使用另一个字符串填充字符串为指定长度

用户评论:

sergey (12-Oct-2011 10:45)

You can use trim functions for clearpad string:

ltrim("0001230", "0") -> 1230
rtrim("0123000", "0") -> 0123
trim("0012300")     -> 123

gene at swipesy dot com (25-Sep-2011 05:18)

This is how I pad using &nbsp; :

str_replace(" ", "&nbsp;&nbsp;", str_pad($foo, 10, " ", STR_PAD_LEFT))

Seems to work well using two &nbsp; tags for each character added, at least for my use. YMMV.

goellerk at bucks dot edu (07-Jun-2010 08:43)

Apparently, as of 5.3.2 the notations "STR_PAD_LEFT" and "STR_PAD_RIGHT" are case sensitive.

$yr = "10";
$yr = str_pad($yr,2,'0',str_pad_left);
print "yr = '$yr'";
yr = '  '

$yr = "10";
$yr = str_pad($yr,2,'0',STR_PAD_LEFT);
print "yr = '$yr'";
yr = '10'

hernanc (24-Apr-2009 04:45)

To get Monday and Sunday's dates of the current week in Y-m-d format  do:

<?php
$mon_date = date('Y-m-d',strtotime(date('Y') . 'W' . str_pad(date('W'), 2, '0',STR_PAD_LEFT) .'1'));
$sun_date =  date('Y-m-d',strtotime(date('Y') . 'W' . str_pad(date('W'), 2, '0',STR_PAD_LEFT).'7'));
?>

Kari &#34;Haprog&#34; Sderholm (21-Mar-2009 02:43)

Here's a quick and simple way to make an mb_str_pad function that works when you have correctly set your internal encoding.

I'm not sure how well this works in all possible scenarios but atleast it worked for me using UTF-8 as internal encoding and using this function on strings containing scandinavian characters "??????" that are double byte in UTF-8.

<?php
function mb_str_pad($input, $pad_length, $pad_string=' ', $pad_type=STR_PAD_RIGHT) {
    $diff = strlen($input) - mb_strlen($input);
    return str_pad($input, $pad_length+$diff, $pad_string, $pad_type);
}
?>

matrebatre (16-Oct-2008 07:28)

Here is a simple function to convert numbers into strings like this:

0 => 0000
1 => 0001
20 => 0020
432 => 0432

<?php

function number_pad($number,$n) {
return str_pad((int) $number,$n,"0",STR_PAD_LEFT);
}

?>

$n indicates how many characters you want.

albert dot serra at camaleongroup dot com (22-Jul-2008 02:36)

<?php
/** Description
   * padclear, clear a pad varchar(9) "*****HOME" -> varchar(4) "HOME"
   * _no use for INT_ : varchar(5) "00100" -> int(3) "100", use $number = (int) "00100";
   *
   * @param string, string original
   * @param char, character to replace
   * @param charreplace, final character
   * @param type, [STR_PAD_RIGHT|STR_PAD_LEFT] see str_pad
   * @return string, transformed string with charreplace
   */
  function padclear($string, $char, $charreplace = null,$type = STR_PAD_RIGHT) {

      $strlen = strlen($string) - 1;
      $i = ($type == STR_PAD_RIGHT) ? 0 : $strlen;
      $stop = ($type == STR_PAD_RIGHT) ? $strlen : 0;
      $difpos = null;
      while(is_null($difpos) && $i != $stop) {
        $difpos = ($string[$i] != $char) ? $i : null;
        if($type == STR_PAD_RIGHT) $i++;
        else $i--;
      }

      if($type == STR_PAD_RIGHT) {
        $ant = str_replace($char,$charreplace,substr($string,0,$difpos));
         $nxt = substr($string,$difpos,$strlen);
      } else {
        $ant = substr($string,0,$difpos);
        $nxt = str_replace($char,$charreplace,substr($string,$difpos,$strlen));
      }

      return $ant . $nxt;
  }

  $string = "HOME*******";
  echo padclear($string,'*','',STR_PAD_LEFT);  // HOME
  $string = "*****HOME";
  echo padclear($string,'*','',STR_PAD_RIGHT); // HOME
?>

bxi at apparoat dot nl (20-Mar-2008 02:17)

In case you want to pad 2 strings together with a character you can use:

<?php
function pad_between_strings($string1, $string2, $length, $char = " ") {
    $fill_length = $length - ( strlen($string1) + strlen($string2) );
    return $string1 . str_repeat($char, $fill_length) . $string2;
}
?>

Spudley (18-Jul-2007 04:47)

Warning: If your string includes non-ascii characters (eg the British pounds sign), str_pad() will treat these as two characters when calculating the padding.

So for example:
<?php
str_pad($currency_symbol.$showtottopay,12," ",STR_PAD_LEFT);
?>
will produce a different length string depending on whether $currency_symbol is pounds or dollars.

Hope this helps someone -- it caused me a lot of problems with misaligned columns in my invoices until I worked it out.

christian dot reinecke at web dot de (01-Apr-2007 06:43)

Fills the first argument (mostly a number, f.e. from a <select> loop to display a date or time) with zeroes.

<?php
function zerofill($mStretch, $iLength = 2)
{
    $sPrintfString = '%0' . (int)$iLength . 's';
    return sprintf($sPrintfString, $mStretch);
}
?>

sprintf() is indeed faster than str_pad.

Charles (05-Dec-2006 11:53)

More corrections to the original flap / Tomek Krzeminski code below (well someone has to check it!) -- the code is a bit mangled but it is still the same:

<?php

function mb_str_pad($ps_input, $pn_pad_length, $ps_pad_string = " ", $pn_pad_type = STR_PAD_RIGHT, $ps_encoding = NULL) {
  $ret = "";

  if (is_null($ps_encoding))
    $ps_encoding = mb_internal_encoding();

  $hn_length_of_padding = $pn_pad_length - mb_strlen($ps_input, $ps_encoding);
  $hn_psLength = mb_strlen($ps_pad_string, $ps_encoding); // pad string length
  
  if ($hn_psLength <= 0 || $hn_length_of_padding <= 0) {
    // Padding string equal to 0:
    //
    $ret = $ps_input;
    }
  else {
    $hn_repeatCount = floor($hn_length_of_padding / $hn_psLength); // how many times repeat

    if ($pn_pad_type == STR_PAD_BOTH) {
      $hs_lastStrLeft = "";
      $hs_lastStrRight = "";
      $hn_repeatCountLeft = $hn_repeatCountRight = ($hn_repeatCount - $hn_repeatCount % 2) / 2;

      $hs_lastStrLength = $hn_length_of_padding - 2 * $hn_repeatCountLeft * $hn_psLength; // the rest length to pad
      $hs_lastStrLeftLength = $hs_lastStrRightLength = floor($hs_lastStrLength / 2);      // the rest length divide to 2 parts
      $hs_lastStrRightLength += $hs_lastStrLength % 2; // the last char add to right side

      $hs_lastStrLeft = mb_substr($ps_pad_string, 0, $hs_lastStrLeftLength, $ps_encoding);
      $hs_lastStrRight = mb_substr($ps_pad_string, 0, $hs_lastStrRightLength, $ps_encoding);

      $ret = str_repeat($ps_pad_string, $hn_repeatCountLeft) . $hs_lastStrLeft;
      $ret .= $ps_input;
      $ret .= str_repeat($ps_pad_string, $hn_repeatCountRight) . $hs_lastStrRight;
      }
    else {
      $hs_lastStr = mb_substr($ps_pad_string, 0, $hn_length_of_padding % $hn_psLength, $ps_encoding); // last part of pad string

      if ($pn_pad_type == STR_PAD_LEFT)
        $ret = str_repeat($ps_pad_string, $hn_repeatCount) . $hs_lastStr . $ps_input;
      else
        $ret = $ps_input . str_repeat($ps_pad_string, $hn_repeatCount) . $hs_lastStr;
      }
    }

  return $ret;
  }

?>

rafaeljaquestudojunto at gmail dot com (11-Sep-2006 01:43)

Looking forward to make some dynamic tabulation, i've noticed that the output appeared twice. I suppose that the parser recognize \t, \n and any other special character as a single character...

So.. If you need 4 tabulatins, just make...

<?php

print str_pad('',4,"\t");

?>

Silvio Ginter (silvio dot ginter at gmx dot de) (15-Nov-2005 04:43)

Hello,

for anyone who needs this, I wrote this extension to str_pad. For details, just look at the comments.

<?php

$string = 'this is a test';
$oldLen = strlen($string);
$direction = STR_PAD_BOTH;
echo $string.'<br>';
echo str_const_len($string, 101, '#', $direction).'<br>';
echo $string.'<br>';
echo str_const_len($string, $oldLen, '#', $direction).'<br>';
echo $string.'<br><br>'."\n";

   
   
/*     This function is an extension to str_pad, it manipulates the referenced
    string '$str' and stretches or reduces it to the specified length. It
    returns the number of characters, that were added or stripped. */
function str_const_len(&$str, $len, $char = ' ', $str_pad_const = STR_PAD_RIGHT) {
    $origLen = strlen($str);
    if (strlen($str) < $len) {     /* stretch string */
        $str = str_pad($str, $len, $char, $str_pad_const);
    }
    else {                         /* reduce string */
        switch ($str_pad_const) {
            case STR_PAD_LEFT:
                $str = substr($str, (strlen($str) - $len), $len);
                break;
            case STR_PAD_BOTH:
                $shorten = (int) ((strlen($str) - $len) / 2);
                $str = substr($str, $shorten, $len);
                break;
            default:
                $str = substr($str, 0, $len);
                break;
        }
    }
    return ($len - $origLen);
}
?>

private dot email at optusnet dot com dot au (10-Aug-2005 01:04)

I wrote these 3 functions that live in a library i include in every programme. I find them useful, and the syntax is easy.

<?php

$str = "test";

function str_pad_right ( $string , $padchar , $int ) {
    $i = strlen ( $string ) + $int;
    $str = str_pad ( $string , $i , $padchar , STR_PAD_RIGHT );
    return $str;
}
   
function str_pad_left ( $string , $padchar , $int ) {
    $i = strlen ( $string ) + $int;
    $str = str_pad ( $string , $i , $padchar , STR_PAD_LEFT );
    return $str;
}
   
function str_pad_both ( $string , $padchar , $int ) {
    $i = strlen ( $string ) + ( $int * 2 );
    $str = str_pad ( $string , $i , $padchar , STR_PAD_BOTH );
    return $str;
}

echo str_pad_left ( $str , "-" , 3 ); // Produces: ---test
echo str_pad_right ( $str , "-" , 3 ); // Produces: test---
echo str_pad_both ( $str , "-" , 3 ); // Produces: ---test---
?>

Hope this can help someone!

zubfatal <root at it dot dk> (28-Mar-2005 05:28)

<?php
    /**
     * str_pad_html - Pad a string to a certain length with another string.
     * accepts HTML code in param: $strPadString.
     *
     * @name        str_pad_html()
     * @author        Tim Johannessen <root@it.dk>
     * @version        1.0.0
     * @param        string    $strInput    The array to iterate through, all non-numeric values will be skipped.
     * @param        int    $intPadLength    Padding length, must be greater than zero.
     * @param        string    [$strPadString]    String to pad $strInput with (default: &nbsp;)
     * @param        int        [$intPadType]        STR_PAD_LEFT, STR_PAD_RIGHT (default), STR_PAD_BOTH
     * @return        string    Returns the padded string
    **/
    function str_pad_html($strInput = "", $intPadLength, $strPadString = "&nbsp;", $intPadType = STR_PAD_RIGHT) {
        if (strlen(trim(strip_tags($strInput))) < intval($intPadLength)) {
           
            switch ($intPadType) {
                 // STR_PAD_LEFT
                case 0:
                    $offsetLeft = intval($intPadLength - strlen(trim(strip_tags($strInput))));
                    $offsetRight = 0;
                    break;
                   
                // STR_PAD_RIGHT
                case 1:
                    $offsetLeft = 0;
                    $offsetRight = intval($intPadLength - strlen(trim(strip_tags($strInput))));
                    break;
                   
                // STR_PAD_BOTH
                case 2:
                    $offsetLeft = intval(($intPadLength - strlen(trim(strip_tags($strInput)))) / 2);
                    $offsetRight = round(($intPadLength - strlen(trim(strip_tags($strInput)))) / 2, 0);
                    break;
                   
                // STR_PAD_RIGHT
                default:
                    $offsetLeft = 0;
                    $offsetRight = intval($intPadLength - strlen(trim(strip_tags($strInput))));
                    break;
            }
           
            $strPadded = str_repeat($strPadString, $offsetLeft) . $strInput . str_repeat($strPadString, $offsetRight);
            unset($strInput, $offsetLeft, $offsetRight);
           
            return $strPadded;
        }
       
        else {
            return $strInput;
        }
    }

?>

tacomage at NOSPAM dot devilishly-deviant dot net (08-Jul-2004 04:04)

If you want to pad a string to a certain screen length with &nbsp; or other HTML entities, but don't want to risk messing up any HTML characters inside the string, try this:

<?php
function str_pad_as_single($input, $len, $pad, $flag=STR_PAD_RIGHT)
{
  $trans=array('$'=>$input,' '=>$pad);
  $output=str_pad('$',$len-strlen($input)+1,' ',$flag);
  $output=strtr($output,$trans);
  return $output;
}
echo str_pad_as_single('<img src="some.gif">',22,'&nbsp;');
// will output <img src="some.gif">&nbsp;&nbsp;

echo str_pad_as_single('<img src="some.gif">',22,'&nbsp;',STR_PAD_BOTH);
// will output &nbsp;<img src="some.gif">&nbsp;

echo str_pad_as_single('<img src="some.gif">',22,'&nbsp;',STR_PAD_LEFT);
// will output &nbsp;&nbsp;<img src="some.gif">
?>

It works by using single characters for str_pad, then replacing the characters with the full strings using strtr, so the two strings can't interfere with each other.  It also conveniently has the same syntax as str_pad.  Yes, I realize that spacing an image with text isn't the best idea, but it's just an example, it'll apply to other HTML as well :-P

giorgio dot balestrieri at mail dot wind dot it (09-Mar-2004 04:49)

For number formatting (like writing numbers with leading zeroes etc.) , sprintf is much faster than str_pad.
Consider the following snippet (it take some minutes to run):

<?php
  echo "str_pad test started, please wait...\n";
 
  $intStart = time();
  for ($idx = 1; $idx <= 10000000; $idx++)
    $strFoo = str_pad($idx, 10, "0", STR_PAD_LEFT);
  $intEnd = time();
 
  echo "str_pad cycle completed in " . ($intEnd - $intStart) . " seconds\n";
  echo "sprintf test started, please wait...\n"; 
 
  $intStart = time();
  for ($idx = 1; $idx <= 10000000; $idx++)
    $strFoo = sprintf("%010d", $idx);
  $intEnd = time();
 
  echo "sprintf cycle completed in " . ($intEnd - $intStart) . " seconds\n";
?>

The str_pad cyle runs 80-100% slower on my pc...

bob [at] bobarmadillo [dot] com (03-Dec-2002 05:22)

In a lot of cases you're better off using str_repeat if you want to use something like   - it repeats the entire string.

Using str_repeat, I wrote a full string pad function that should closely mimic str_pad in every other way:

<?php
function full_str_pad($input, $pad_length, $pad_string = '', $pad_type = 0) {
 $str = '';
 $length = $pad_length - strlen($input);
 if ($length > 0) { // str_repeat doesn't like negatives
  if ($pad_type == STR_PAD_RIGHT) { // STR_PAD_RIGHT == 1
   $str = $input.str_repeat($pad_string, $length);
  } elseif ($pad_type == STR_PAD_BOTH) { // STR_PAD_BOTH == 2
   $str = str_repeat($pad_string, floor($length/2));
   $str .= $input;
   $str .= str_repeat($pad_string, ceil($length/2));
  } else { // defaults to STR_PAD_LEFT == 0
   $str = str_repeat($pad_string, $length).$input;
  }
 } else { // if $length is negative or zero we don't need to do anything
  $str = $input;
 }
 return $str;
}

$pad_me = "Test String";
echo '|'.full_str_pad($pad_me, 20, ' ')."|\n";
echo '|'.full_str_pad($pad_me, 20, ' ', STR_PAD_RIGHT)."|\n";
echo '|'.full_str_pad($pad_me, 20, ' ', STR_PAD_BOTH)."|\n";
?>

david dot rensonnet at swing dot be (02-Dec-2002 11:18)

my solution to saveloywill at netscape dot net:

$myvar2="Alien";
$myvar=str_pad($myvar2,15," ",STR_PAD_RIGHT);
$myvar=str_replace(" ","&nbsp;",$myvar);

this way, only complete spaces will show up.

enjoy!
david rensonnet

Fahad dot Gilani at anu dot edu dot au (02-Dec-2002 10:22)

Basically, *all* of you guys have a 'long' way of padding text with html tags (which includes &nbsp;) You dont even have to do a str_replace... try the following code and this will work with ANY html tag there is out there and you don't have to worry about tag character lengths so on and so forth:
<?
  $text = "This is pretty interesting!";
  $pad_string = "&nbsp;";
 
  //Pad text on both sides
  $text = str_pad($text, strlen($text)+(20*strlen($pad_string)), $pad_string, STR_PAD_BOTH);
  print $text." Dont you think?";
?>
Will produce:
          This is pretty interesting!           Dont you think?

Cheers,
Fahad

no dot spam at no dot spam dot no (27-Sep-2002 12:28)

there could already be spaces in the string.

1) strlen the string
2) replace spaces with "AUniqueString"
3) strlen the new string
4) compare the two strlen's
5) pad as needed considering the new strlen
6) finally, replace all "AUniqueString" 's with &nbsp; 's

hack & a half, slow as well i bet

cd579 at hotmail dot com (22-Aug-2002 09:53)

Why not just use a space[' '] instead of a character that COULD be inside the string, and risk messing it up?  Example:

$string = 'test';

$string = str_pad($string, 10, " ", STR_PAD_BOTH);
// $string now equals '      test'

$string = str_replace(" ", "&nbsp;", $string);

mreilly at NOSPAM dot mac dot com (20-Aug-2002 07:23)

When provided with a string of characters as the pad value, str_pad uses all the characters as fill, and can leave partial strings. (eg. If the pad value is 'ABC' and it needs 5 characters to pad with, it outputs 'ABCAB'.) This is a problem when you want to pad with non-breaking spaces, the code for which is 6 characters long.

This can be resolved by first padding the string with a single character that won't be found in the strings such as * then doing a str_replace of * with &nbsp;.

saveloywill at netscape dot net (10-Aug-2002 08:50)

Here is my solution to the above problem.
Simply place the code in question inbetween  html <pre> tags, like this:

<?php
print "<pre>";
$input = "Alien";
print str_pad($input, 10);
print "*";
print "</pre>";
?>

Thanks.

pozytron#mac#com (08-Jul-2002 10:20)

The trouble with cj@NOSPAM.ceejayoz.com's version over pestilenc@hotmail.com's is that many of the times it is used, it will end up with fragments of the "&nbsp;" code.

For example, the following code:
<?php
echo str_pad("TESTSTRING",60,"&nbsp;",STR_PAD_BOTH);
?>

produces the following HTML output:
&nbsp;&nbsp;&nbsp;&nbsp;&TESTSTRING&nbsp;&nbsp;&nbsp;&nbsp;&

cj at NOSPAM dot ceejayoz dot com (17-Jun-2002 08:38)

Another solution to no_email@php.net's problem would be to simply multiply the padding string by 6.

e.g.

$string = str_pad($string, 10, "&nbsp;", STR_PAD_BOTH);

becomes

$string = str_pad($string, 60, "&nbsp;", STR_PAD_BOTH);

which will avoid problems with the above solution, which will mess up text that has the * in it (or whichever character you're replacing)

pestilenc at hotmail dot com (06-Jun-2002 12:26)

For me this worked.
$string = 'help';

#First, str_pad() with unique character.
$string = str_pad($string, 10, "*", STR_PAD_BOTH);
#$string = '***help***';

#Second, str_replace with '&nbsp;'
$string = str_replace("*", "&nbsp;", $string);

no_email at php dot net (30-May-2002 06:34)

To convert your string couldnt you just use strval($var)?

What if you want non-breaking spaces? If I try to str_pad with "&nbsp;" PHP thinks my padding string is 6 characters, whn in HTML it is only one.

jared at dctkc dot com (04-May-2002 12:25)

matthew.somerville's code did NOT work for me.
neither did bert@catsburg.com's.
neither did any other documentation.
(if I isolated the code by itself, they all worked; but in the context I was using it, $value was numeric, and there is NO WAY to force it to be a string in PHP).

I had to roll my own. I used 'trim' to _force_
the value of $value to be string, because as
long as PHP thought it was numeric, I could
not use any form of left-padding with zeros.

This worked (I use sprintf to left-pad
$value with zeros to a length of 4):

sprintf("%04s",trim($value));

matthew dot somerville at trinity dot oxford dot ac dot uk (05-Aug-2001 02:53)

I find:

$mystr = substr("0000$mystr",-4)

(where the 0s are padding characters and -4 is the negative of the maxlength to pad to) is even simpler.