preg_replace help ??

PHPycho

Hello forums!!
Case:

$db_row = array('name_field' => 'Tom', 'roll_field' => 22) ; //items from db

$string = 'my/name/[name_field]/roll/[roll_field]';

$final_string = preg_replace('/(\[(.*?)\])/',$db_row['$2'], $string); //I tried this, but gives notice error: Undefined index:  $2

echo $final_string; // expected output: my/name/Tom/roll/22

How to accomplish this using preg_replace.
Thanks.

nrg_alpha

This is because $2 does not exist.. The way preg works, is that every set of capturing brackets (from left to right), stores what it matches starting with variable $1, $2, etc... since you only have one set of capturing brackets ([(.*?)]), the value it matches is stored into $1, so you need to use that instead.. I suspect another issue might be that you have an array $db_row with a key named $2, and that preg thinks you are trying to insert 'the second captured value' in place of $2.. but obviously, there is no second capture.. (I'll get to this in a code sample at the bottom).

Also, note that both [name_field] and [roll_field] will be replaced with whatever value you are looking to replace it with in your current pattern, as preg_replace will find all instances of [....] and replace that. If you need to target just the first one by example, explicitly point that out in the preg pattern.. so for example:

$string = 'my/name/[name_field]/roll/[roll_field]';
$db_row['$2'] = 'whatever!';
$finalstring = preg_replace('#\[name_field\]#', $db_row["$2"], $string);

Output (when echo'ing $finalstring):

my/name/whatever!/roll/[roll_field]

Is that along the lines of what you are looking for?

EDIT - Obviously, if you do want to replace all instances of [...], you can use: #[[^]]+]# as your pattern instead.

nrg_alpha

Oops.. I just realized there are two captures in your initial pattern.. (this is the price I pay for checking stuff too early in the morning!) Let me know if I am on the right track with my code suggestion though.. sorry about the incorrect explanation on my part.. I did get that wrong.

PHPycho

Here is the awsome solution found so far:

<?php
$db_row = array('name_field' => 'Tom', 'roll_field' => 22) ; //items from db

$string = 'my/name/[name_field]/roll/[roll_field]';

$final_string = preg_replace('/\[(.*?)\]/e','$db_row["$1"]', $string); //I tried this, but gives notice error: Undefined index:  $2

echo $final_string; // expected output: my/name/Tom/roll/22
?>

Are there any alternatives ?
Thanks

nrg_alpha

Ok.. I think I got it... let me know if this is what you are looking for...

$db_row = array('name_field' => 'Tom', 'roll_field' => 22); //items from db 
$string = 'my/name/[name_field]/roll/[roll_field]';
$finalString = preg_replace('#([^[]+)(?:\[name_field\])([^[]+)(?:\[roll_field\])#', '$1'.$db_row['name_field'].'${2}'.$db_row['roll_field'], $string);
echo $finalString;

Output:

my/name/Tom/roll/22