CODEWITHSUNDEEP
phparraysloops
Peter Oram
Peter Oram

Reputation: 6738

for vs foreach - reference to array elements

I had an array which contained lines of a file that I had to process, each element of the array was a line of the file. After processing I implode the file, write it out and use it.

When I tried to use foreach for this, it didn't work. I had a suspicion that it was creating a copy of the element rather than referencing the element directly, so used a for loop instead, which did work.

My question is, is there some way to use a foreach loop in this scenario or when redefining elements of an array must you always use a for loop?

Example code:

$fileArray = file('blah.txt');
foreach ($fileArray as $thisLine) {
    if ( condition ) {
        $thisLine = "changed state";
    }
}
$newFileArray = implode('',$fileArray);

Didn't work vs:

$fileArray = file('blah.txt');
for ($x=0;$x<count($fileArray);$x++) {
    if ( condition ) {
        $fileArray[$x] = "changed state";
    }
}
$newFileArray = implode('',$fileArray);

Which worked fine.

Upvotes: 0

Views: 97

Answers (2)

Matt S
Matt S

Reputation: 15374

In your first example, you're altering a copy of a string. $thisLine is not a reference to the element in the array, but a copy of the array element.

In your second example, you are altering the array directly. You could use a foreach, but only if you go back to referencing the array:

foreach ($fileArray as $key => $thisLine) {
    if ( condition ) {
        $fileArray[$key] = "changed state";
    }
}

Upvotes: 0

jeroen
jeroen

Reputation: 91734

$fileArray = file('blah.txt');
foreach ($fileArray as $key => $thisLine) {
    if ( condition ) {
        $fileArray[$key] = "changed state";
    }
}
$newFileArray = implode('',$fileArray);

or passing by reference directly:

$fileArray = file('blah.txt');
foreach ($fileArray as &$thisLine) {
    if ( condition ) {
        $thisLine = "changed state";
    }
}
$newFileArray = implode('',$fileArray);

Upvotes: 3

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