Replace everything from beginning of line to equal sign - php

Question

For a content with the format:
KEY=VALUE
like:
LISTEN=I am listening.
I need to do some replacing using regex. I want this regular expression to replace anything before the = with $key (making it have to be from beginning of line so a key like 'EN' wont replace a key like "TOKEN".
Here's what I'm using, but it doesn't seem to work:
$content = preg_replace('~^'.$key.'\s?=[^\n$]+~iu',$newKey,$content);

Answer 1

$content = "foo=one\n"
. "bar=two\n"
. "baz=three\n";
$keys = array(
'foo' => 'newFoo',
'bar' => 'newBar',
'baz' => 'newBaz',
);
foreach ( $keys as $oldKey => $newKey ) {
$oldKey = preg_quote($oldKey, '#');
$content = preg_replace("#^{$oldKey}( ?=)#m", "{$newKey}\\1", $content);
}
echo $content;
Output:
newFoo=one
newBar=two
newBaz=three

Answer 2

$str = 'LISTEN=I am listening.';
$new_key = 'ÉCOUTER';
echo preg_replace('/^[^=]*=/', $new_key . '=', $str);

Answer 3

If I understood your question well, you need to switch the multi-line mode on using m modifier.
$content = preg_replace('/^'.preg_quote($key, '/').'(?=\s?=)/ium', $newKey, $content);
By the way I do recommend to escape the $key using preg_quote to avoid unexpected results.
So if the source content is this:
KEY1=VALUE1
HELLO=WORLD
KEY3=VALUE3
The result will be this (if $key=HELLO and $newKey=BYE):
KEY1=VALUE1
BYE=WORLD
KEY3=VALUE3

Answer 4

This should do the trick.
\A is the start of a line, and the parentheses is for grouping things to keep/replace.
$new_content = preg_replace("/\A(.*)(=.*)/", "$key$2", $content);

Answer 5

$content = 'LISTEN=I am listening.';
$key = 'LISTEN';
$newKey = 'NEW';
$content = preg_replace('~^'.$key.'(\s?=)~iu',$newKey.'$1',$content);
echo $content;
output is NEW=I am listening.
But is does not change on a partial match
$content = 'LISTEN=I am listening.';
$key = 'TEN';
$new_key = 'NEW';
$content = preg_replace('~^'.$key.'(\s?=)~iu',$newKey.'$1',$content);
echo $content;
Output is LISTEN=I am listening.