Question

I have an array of user inputs ($atts) as key=>value pairs. Some of the values could be written as an array expression, such as:

'setting' => 'array(50,25)'

In those cases, I would like to convert the array expression contained in that string into an actual array. So the output would be something like:

$atts = array(
'setting' => array(50,25),
'another' => 'not written as an array expression'
)

Written logically, the code would be:

For each key=>value pair in the array $atts…
if the value is a string formatted as an array expression…
explode that value into an array.

Anybody know how I would write this in PHP?

Answer 1

Use the tokenizer:

function stringToArray($str) {
    $array = array();
    $toks = token_get_all("<?php $str");

    if ($toks[1][0] != T_ARRAY || $toks[2] != '(' || end($toks) != ')')
        return null;

    for($i=3; $i<count($toks)-1; $i+=2) {
        if (count($toks[$i]) != 3)
            return null;

        if ($toks[$i][0] == T_WHITESPACE) {
            $i--;
            continue;
        }

        if ($toks[$i][0] == T_VARIABLE || $toks[$i][0] == T_STRING)
            return null;

        $value = $toks[$i][1];
        if ($toks[$i][0] == T_CONSTANT_ENCAPSED_STRING)
            $value = substr($value, 1, strlen($value) - 2);

        $array[] = $value;

        if ($toks[$i + 1] != ',' && $toks[$i + 1] != ')' && $toks[$i + 1][0] != T_WHITESPACE)
            return null;
    }

    return $array;
}

The above will work only for literals. Passing a variable, a constant, an expression, a nested array or a malformed array declaration will return null:

stringToArray('array(1,2)');              // works
stringToArray('array(1,2.4)');            // works
stringToArray('array("foo",2)');          // works
stringToArray('array(\'hello\',2)');      // works
stringToArray('array()');                 // works
stringToArray('array(1,2 + 3)');          // returns null
stringToArray('array(1,2 + 3)');          // returns null
stringToArray('array("foo"."bar")');      // returns null
stringToArray('array(array("hello"))');   // returns null
stringToArray('array($a,$b)');            // returns null
stringToArray('array(new bar)');          // returns null
stringToArray('array(SOME_CONST)');       // returns null
stringToArray('hello');                   // returns null

You can also use the following to check if your string is an array expression or not:

function isArrayExpression($str) {
    $toks = token_get_all("<?php $str");
    return (
        $toks[1][0] == T_ARRAY &&
        $toks[2] == '(' &&
        end($toks) == ')'
    );
}

isArrayExpression('array(1,2,3)');         // true
isArrayExpression('array is cool');        // false
isArrayExpression('array(!!!!');           // false

You can always tweak it to your needs. Hope this helps.