Setting up PHP nested variable

Question

I have the following code that works:

$apple_color = "red";
$pear_color = "green";
$banana_color = "yellow";
$grape_color = "purple";

foreach(array("apple","pear","banana","grape") as $idx=>$fname) {
    $var = "${fname}_color";
    echo "$var = ${$var}<br>".PHP_EOL;
}

However, I cannot figure out how to shorten the code by eliminating the $var variable to something like this:

foreach(array("apple","pear","banana","grape") as $idx=>$fname) {
    echo "${fname}_color = ${${fname}_color}<br>".PHP_EOL;
}

The "${${fname}_color" returns an PHP error that says "syntax error, unexpected '_color' (T_STRING)"

PHP Fiddle: http://phpfiddle.org/lite/code/wrfp-yqkx

Oleg Dubas · Accepted Answer · 2017-05-24 16:24:11Z

1

How about this? Use ${'string'} construction

foreach(["apple","pear","banana","grape"] as $fname) {
    echo "{$fname}_color = ".${$fname.'_color'}."<br>".PHP_EOL;
}

answered May 24, 2017 at 16:24

Oleg Dubas

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Comments

Don't Panic · Accepted Answer · 2017-05-24 16:59:16Z

1

Instead of having a separate variable for each color, store the colors in an array indexed by the fruit name. This way you can avoid the mess of using variable variables.

$colors = [
    'apple' => 'red',
    'pear' => 'green',
    'banana' => 'yellow',
    'grape' => 'purple'
];

foreach (["apple","pear","banana","grape"] as $fname) {
    echo "{$fname}_color = $colors[$fname]<br>".PHP_EOL;
}

answered May 24, 2017 at 16:59

Don't Panic

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1 Comment

Scott Over a year ago

Your idea works, however, in my situation, I have no control over the initial variable names that is passed into my code.

rickdenhaan · Accepted Answer · 2017-05-24 16:25:10Z

0

Use string formatting to simplify your life:

echo sprintf('$%s_color = %s<br>' . PHP_EOL, $fname, ${$fname . '_color'});

answered May 24, 2017 at 16:25

rickdenhaan

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