How to change first occurrence of word in a string


How do I do to change the first occurrence of a word in a string?


$a = "Yo! **Hello** this is the first word of Hello in this sentence";


$b = "Yo! **Welcome** this is the first word of Hello in this sentence";

This works, although a bit inefficient:

$a = "Yo! **Hello** this is the first word of Hello in this sentence"; $a = preg_replace('/Hello/', 'Welcome', $a, 1);

The other popular answer:

$b = str_replace('Hello', 'Welcome', $a, 1);

does not work. The fourth argument of str_replace should be a variable, which is passed by reference and str_replace will set it to the <em>number of replacements made</em>.

A better solution would be to extract two sub-strings from the input string:

<ol><li>Sub-string before the first occurrence of Hello, call it $s1</li> <li>Sub-string after the first occurrence of Hello, call it $s2</li> </ol>

One can use the strpos to get the position.

Result is $s1.'Welcome'.$s2


Just use substr twice with strpos.

$a = "Yo! **Hello** this is the first word of Hello in this sentence"; $search = "Hello"; $replacement = "Welcome"; $b = substr( $a, 0, strpos( $a, $search)) . $replacement . substr( $a, strpos( $a, $search) + strlen( $search));



This is the best for compactness and performances:

if(($offset=strpos($string,$replaced))!==false){ $string=substr_replace($replaced,$replacer,$offset,strlen($replaced)); }

Replace only the first occurrence without the overload of the regular expressions


Use substr_replace().


Use str_replace('Hello','Welcome',$a,1);


Build It:

function str_replace_first($search, $replace, $source) { $explode = explode( $search, $source ); $shift = array_shift( $explode ); $implode = implode( $search, $explode ); return $shift.$replace.$implode; }

Call it:

$msg = "Yo! **Hello** this is the first word of Hello in this sentence"; echo str_replace_first( 'Hello', 'Welcome', $msg );

Try It:




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