Function to replace first occurence only.

Posted on 2006-03-29
Last Modified: 2010-05-16

I'm after a function to replace the first occurance of string only, with a replacement string..

basically ,str_replace but only for the first occurance, not all..

Anyone up for it?
Question by:Coolkill
    LVL 49

    Expert Comment

    When your php version is right, you can use a 4th parameter to str_replace:

    $string = str_replace($old,$new,$string,1);

    Otherwise, try this quick and dirty one:

    $string = implode('newstring', explode('occurance', $string, 2));

    LVL 8

    Accepted Solution

    Or the method for optimum customisation and backwards compatibility (this works in PHP 4 and above):
    $string = preg_replace($pattern, $replace, $string, 1);

    Look at the php manual:
    LVL 40

    Expert Comment

    Roonaan is not correct.

    The 4th parameter is used to return the number of times it was replaced, not to control how many times it was replaced. Notice the & in the function definition. This is an output property, not an input property. Though I DO think it should act as both!


    $count = 2;
    $str = str_replace("ll", "", "good golly miss molly dolly!", $count);
    echo $count . ' ' . $str;

    Roonaan would be expecting output of ...

    2 good goy miss moy dolly!

    The actual output is ...

    3 good goy miss moy doy!

    Trying to run the code with a hard-coded value in the place of $count results in ...

    Fatal error: Only variables can be passed by reference in C:\d6.php on line 3

    To only replace the first occurance of a substring then use the preg_replace() function as described by kebabs.
    LVL 40

    Expert Comment

    And just in case Roonaan wants to know what version I'm on ...

    <29/03/2006 14:04:30 C:\>php -v
    PHP 5.1.3-dev (cli) (built: Feb 20 2006 00:29:25)
    Copyright (c) 1997-2006 The PHP Group
    Zend Engine v2.1.0, Copyright (c) 1998-2006 Zend Technologies
        with Zend Extension Manager v1.0.10, Copyright (c) 2003-2006, by Zend Technologies
        with Zend Optimizer v3.0.0-Beta2, Copyright (c) 1998-2006, by Zend Technologies

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