Convert dot syntax like “this.that.other” to multi-dimensional array in PHP

I am pretty sure you are trying to do this to store some configuration data or similar.

I highly suggest you to save such file as .ini and use parse_ini_file() function to change the configuration data into a multidimensional array. As simple as this

$confArray = parse_ini_file("filename.ini"); 
var_dump($confArray);

Although pasrse_ini_file() can also bring out multidimensional array, I will present a different solution. Zend_Config_Ini()

$conf = new Zend_COnfig_Ini("path/to/file.ini");
echo $conf -> one -> two -> three; // This is how easy it is to do so
//prints one.two.three

You can use this function to achieve desired result. It uses php eval() function, despite on there historically a lot of doubts related to it

function ini($file) {

    // Parse ini file
    $ini = parse_ini_file($file, true);

    // Foreach section
    foreach ($ini as $sectionName => $sectionParamA) {

        // Foreach param within section
        foreach ($sectionParamA as $sectionParamK => $sectionParamV) {

            // If param name contains '.'
            if (preg_match('/\./', $sectionParamK)) {

                // Get the levels
                $levelA = explode('.', $sectionParamK);

                // Declare/reset the $depth array
                $depth = array();

                // Foreach level except last level
                for ($i = 0; $i < count($levelA) - 1; $i++) {

                    // Build the list of parent array dimensions
                    for ($d = 0; $d < count($depth); $d++)
                        $depth[$d] = str_replace('$i', '$i-' . ($i - $d), $depth[$d]);

                    // Append current array dimension
                    $depth[] = '[$levelA[$i]]';

                    // Check if current-level value is already an array
                    // (so it mean this it contains key-value pairs) and if so -
                    if (eval('return is_array($sectionParamA' . implode('', $depth) . ');')) {

                        // If the value of the param at certain-depth-level dimension is not yet an instance
                        // of ArrayObject class
                        if (!eval('return is_array($sectionParamA' . implode('', $depth) . '[' . $levelA[$i+1]. ']);'))

                            // Setup it
                            eval('$sectionParamA' . implode('', $depth) . '[' . $levelA[$i+1]. '] = $sectionParamA[$sectionParamK];');

                        // Else
                    } else {

                        // Setup the param value as a value of certain-depth-level dimension key within array
                        eval('$sectionParamA' . implode('', $depth) . ' = array(
                            $levelA[$i+1] => $sectionParamA[$sectionParamK]
                        );');
                    }
                }

                // Unset orinal param name and it's value, as now param name was parsed and converted
                // to nesting arrays
                unset($sectionParamA[$sectionParamK]);
            }
        }

        // Update section
        $ini[$sectionName] = $sectionParamA;
    }

    // Return
    return $ini;
}

Quick and dirty...

<?php

$input = 'one.two.three = four';

list($key, $value) = explode('=', $input);
foreach (explode('.', $key) as $keyName) {
    if (false === isset($source)) {
        $source    = array();
        $sourceRef = &$source;
    }
    $keyName = trim($keyName);
    $sourceRef  = &$sourceRef[$keyName];
}
$sourceRef = $value;
unset($sourceRef);
var_dump($source);