<?php
// Hi, while using the following code i experienced
// an interesting behaviour of preg_replace():

$string = "Say a [word0] about [word1] and [word2]";

$search[0] ="[word0]";
$search[1]= "[word1]";
$search[2]= "[word2]";

$replace[0]="betterWord0";
$replace[2]="betterWord2";
$replace[1]="betterWord1";

$string2 = preg_replace($search,$replace,$string);

echo "Result is:<BR>" . $string2;
echo "<BR><BR>Result should be:<BR> Say a [betterWord0] about
[betterWord1] and [betterWord2]";

// result should be:
//Say a [betterWord0] about [betterWord1] and [betterWord2]
//
// but produces: 
//Say a [betterWord0] about [betterWord2] and [betterWord1]
//
// Seems like the order in which i build my array
// is the order for replacing...and not the index
// of $array[$index]
//
// if you add a ksort it works fine:

ksort($search,SORT_NUMERIC);
ksort($replace,SORT_NUMERIC);		
reset($search);
reset($replace);		

$string3 = preg_replace($search,$replace,$string);
echo "<BR><BR>Corrected (ksort) Result is:<BR>" . $string3;

//
// Has someone an idea, about what's happening here?
//
// just a guy addicted to php ;-)
?>

The search strings used in the preg_replace() function are regular expressions. "[abc]" is a regular expression which matches any of the characters "a", "b" or "c".

Either use str_replace() to replace your strings, or learn to use regular expressions <http://de3.php.net/manual/en/pcre.pattern.syntax.php>.

Thank you for taking the time to write to us, but this is not
a bug. Please double-check the documentation available at
http://www.php.net/manual/ and the instructions on how to report
a bug at http://bugs.php.net/how-to-report.php

The replacment is done in the order the array was created, if you want it to be done based on array keys that run an appropriate sorting function before executing the preg_replace function.

This could be made more clear in the manual.  I'll add a note and an example tonight.

This bug has been fixed in CVS.

In case this was a PHP problem, snapshots of the sources are packaged
every three hours; this change will be in the next snapshot. You can
grab the snapshot at http://snaps.php.net/.
 
In case this was a documentation problem, the fix will show up soon at
http://www.php.net/manual/.

In case this was a PHP.net website problem, the change will show
up on the PHP.net site and on the mirror sites in short time.
 
Thank you for the report, and for helping us make PHP better.