Replace string only once with php preg_replace

Question

I need a replace string once function and believe preg_match might be my best bet.

I was using this, but due to the dynamicness of use, sometimes this function behaves strangely:

function str_replace_once($remove , $replace , $string)
{
    $pos = strpos($string, $remove);
    if ($pos === false) 
    {
    // Nothing found
    return $string;
    }
    return substr_replace($string, $replace, $pos, strlen($remove));
}

Now I am taking this approach but have ran to to the error listed below.... I'm parsing all kinds of html strings with this function, so its hard to give a value thats causing the error. As of now 80% of my uses of the below show this error .

function str_replace_once($remove , $replace , $string)
{
    $remove = str_replace('/','\/',$remove);
    $return = preg_replace("/$remove/", $replace, $string, 1);  
    return $return;
}

error:

Warning: preg_replace() [function.preg-replace]: Compilation failed: nothing to repeat at offset 0

Can anyone refine a solution?

you've included a limit on the replacements of 1 - do you really just want to replace the first instance of the pattern match? Anyway, I think including this when there is no match may be causing your problem with some replacement patterns. — AJ.
– AJ., Commented Aug 2, 2010 at 23:20
See [ PHP: str_replace that only acts on the first match? ](stackoverflow.com/questions/1252693/…). — Matthew Flaschen
– Matthew Flaschen, Commented Aug 2, 2010 at 23:21

Wrikken · Accepted Answer · 2010-08-02 23:21:01Z

8

You are looking for preg_quote instead of trying to escape the \ yourself (which doesn't take [, + and many others into account):

$return = preg_replace('/'.preg_quote($remove,'/').'/', $replace, $string, 1);

answered Aug 2, 2010 at 23:21

Wrikken

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Danon · Accepted Answer · 2019-06-24 13:50:48Z

0

You can also use T-Regx library:

pattern('[a-z]+')->replace($string)->first()->with($replace);

and also you should not use preg_quote(), as it's not safe - try Prepared Patterns.

answered Jun 24, 2019 at 13:50

Danon

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