php replace substring with regex

Question

Ok, i know there are trillions of similar questions, but i'm finding it really hard to achieve this. I have some strings of this formats:

$x = '<iframe src="[File:19]"></iframe>';
$y = '<img src=[File:2212] />';
$z = '<source src="[File:42]" />';

I'm trying to get the id given after the File: and also replace the whole [File:xxx] with another string. I'm trying like the following, but it seems i can't fully understand the usage of preg_replace.

$file = ('<iframe src="[File:134]"></frame>');
$rex = "/^.*(\[File:[0-9]{1,}\])/i" ;
if ( preg_match($rex, $file, $match) ) {
    echo 'OK';
}
$file = preg_replace ($rex, "http://lala.com/la.pdf", $file);
echo "<br>".htmlentities($file)."<br>";

Could you please give me some hints on how i can do this?

Thanks in advance.

you can use preg_match_all and delete ^.*.. (should work) But actually you should use PHP DOM for this — noob
– noob, Commented Mar 13, 2012 at 14:17

Mr. Llama · Accepted Answer · 2012-03-13 14:20:49Z

1

This should do the trick:

preg_match('/\[File:(\d+)\]/i', $str, $match)

$match[0] will have the whole string, $match[1] will have just the number.
After the regex match, you can use str_replace to remove $match[0] from the string.

Example:

$x = '<iframe src="[File:19]"></iframe>';
preg_match('/\[File:(\d+)\]/i', $x, $match);
var_dump($match);

Gives:

array(2) {
  [0]=>
  string(9) "[File:19]"
  [1]=>
  string(2) "19"
}

answered Mar 13, 2012 at 14:20

Mr. Llama

21k3 gold badges70 silver badges121 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Toto · Accepted Answer · 2012-03-13 14:42:28Z

1

Change these 2 lines

$rex = "/^.*(\[File:[0-9]{1,}\])/i" ;

$file = preg_replace ($rex, "http://lala.com/la.pdf", $file);

to:

$rex = "/^(.*)\[File:[0-9]{1,}\]/i" ;

$file = preg_replace ($rex, "$1http://lala.com/la.pdf", $file);

This will capture what is before [File...] into group 1, then in the replace part, add this group (i.e. $1) in front of the replace string.

It can be rewritten as:

$rex = "/\[File:\d+\]/i" ;

$file = preg_replace ($rex, "http://lala.com/la.pdf", $file);

edited Mar 13, 2012 at 14:42

answered Mar 13, 2012 at 14:20

Toto

91.7k63 gold badges97 silver badges135 bronze badges

2 Comments

Berry Langerak Over a year ago

Is it just me, or is /^(.*)\[File not only a very useless bit, but also very bad for performance? /^.*\[File/ comes down to /\[File, does it not? If you don't capture it in the regex, you don't have to replace it, right?

Toto Over a year ago

@BerryLangerak: Yes, you're right, I've just taken the OP's regex with minimum changes.

Berry Langerak · Accepted Answer · 2012-03-14 08:20:59Z

1

This should work:

<?php
$formats[] = '<iframe src="[File:19]"></iframe>';
$formats[] = '<img src=[File:2212] />';
$formats[] = '<source src="[File:42]" />';


foreach( $formats as $format ) {

    $regex = '~\[File:(\d+)\]~';

    $replace = function( $matches ) {
        return 'http://lala.com/la.pdf?id=' . $matches[1];
    };

    var_dump( preg_replace_callback( $regex, $replace, $format ) );
}

I've created a lambda for the replacement, because I have a feeling you want to use the id after File: instead of just discarding that. Have fun with it. If you have any questions, do tell.

edited Mar 14, 2012 at 8:20

answered Mar 13, 2012 at 14:30

Berry Langerak

18.9k5 gold badges49 silver badges62 bronze badges

1 Comment

Mr. Llama Over a year ago

You don't need to capture the whole expression in parens. By default the whole matched region is stored in $matches[0].

Collectives™ on Stack Overflow

php replace substring with regex

3 Answers 3

Comments

2 Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

2 Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related