PHP Using RegEx(preg match) to get substring of a string

Question

Hi I'm trying to parse a sub string with php preg_match.

String input like :

25k8cp1gl6-Mein Herze  im Blut, BWV 199: Recitative: Ich  Wunden_SVD1329578_14691639_unified :CPN_trans:

Here I want to extract Mein Herze im Blut, BWV 199: Recitative: Ich Wunden

25k8cp1gl6-La Puesta Del Sol_SVD1133599_12537702_unified :CPN_trans:

Here I want to extract La Puesta Del Sol

La Puesta Del Sol_SVD1133599_12537702_unified :CPN_trans:

Here I want to extract La Puesta Del Sol

25k8cp1gl6-La Puesta Del Sol_MNA1133599_12537702_unified :CPN_trans:

Here I want to extract La Puesta Del Sol

25k8cp1gl6-La Puesta Del Sol_IMC1133599_12537702_unified :CPN_trans:

Here I want to extract La Puesta Del Sol

So basically I want to extract the string before _SVD or _MNA and _IMC excluding the first part of the string 25k8cp1gl6-

Thanks in Advance

Sam · Accepted Answer · 2014-05-07 14:53:26Z

2

Here is an expression for ya:

(?<=25k8cp1gl6-).*?(?=_(?:SVD|MNA|IMC))

Explanation:

(?<=...) is syntax for a lookahead, meaning we start by finding (but not including in our match) "25k8cp1gl6-". Then we lazily match our entire string with .*?. Finally, (?=...) is a lookahead syntax. We look for "_" followed by "SVD", "MNA", or "IMC" (separated with | in the non-capturing group (?:...)).

PHP:

$strings = array(
    '25k8cp1gl6-Mein Herze  im Blut, BWV 199: Recitative: Ich  Wunden_SVD1329578_14691639_unified :CPN_trans:',
    '25k8cp1gl6-La Puesta Del Sol_SVD1133599_12537702_unified :CPN_trans:',
    '25k8cp1gl6-La Puesta Del Sol_MNA1133599_12537702_unified :CPN_trans:',
    '25k8cp1gl6-La Puesta Del Sol_IMC1133599_12537702_unified :CPN_trans:',
);

foreach($strings as $string) {
    if(preg_match('/(?<=25k8cp1gl6-).*?(?=_(?:SVD|MNA|IMC))/', $string, $matches)) {
        $substring = reset($matches);
        var_dump($substring);
    }
}

Another option, which would use preg_replace(), is demoed here:

^\w+-(.*?)_(?:SVD|MNA|IMC).*

Explanation:

This one matches the entire string, but captures the part we want to keep so that we can reference it in our replacement. Also note that I began with ^\w+- instead of 25k8cp1gl6-. This pretty much just looks for any number of "word characters" ([A-Za-z0-9_]) followed by a hyphen at the beginning of the string. If it needs to be "25k8cp1gl6-", you can replace this; I just wanted to show another option.

PHP:

$strings = array(
    '25k8cp1gl6-Mein Herze  im Blut, BWV 199: Recitative: Ich  Wunden_SVD1329578_14691639_unified :CPN_trans:',
    '25k8cp1gl6-La Puesta Del Sol_SVD1133599_12537702_unified :CPN_trans:',
    '25k8cp1gl6-La Puesta Del Sol_MNA1133599_12537702_unified :CPN_trans:',
    '25k8cp1gl6-La Puesta Del Sol_IMC1133599_12537702_unified :CPN_trans:',
);

foreach($strings as $string) {
    $substring = preg_replace('/^\w+-(.*?)_(?:SVD|MNA|IMC).*/', '$1', $string);
    var_dump($substring);
}

edited May 7, 2014 at 14:53

answered May 7, 2014 at 14:43

Sam

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7 Comments

Uttam Dutta Over a year ago

First part contains some Alphanumeric characters, so I changed it to (?<=[a-zA-Z0-9_]-)(.*?)(?=_(?:SVD|MNA|IMC)) It's working, Thanks a lot Sam!

Sam Over a year ago

No problem, I added a second alternative. Also note that [a-zA-Z0-9_] is equivalent to \w.

Uttam Dutta Over a year ago

It gives the required sub string correctly if the first part "25k8cp1gl6-" is present, but for my case first part is optional.

Sam Over a year ago

I completely missed that, check out: (?:\w+-)?\K.*?(?=_(?:SVD|MNA|IMC))..I can update/explain if you need

Uttam Dutta Over a year ago

This works great, how about extracting the SVD1133599_12537702 part or IMC1133599_12537702 or MNA1133599_12537702 or SVD1133599 part or IMC1133599 or MNA1133599. here please note that "_12537702" is optional

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