Convert a string into an associative array key?

Question

Given a string that contains values separated by dots:

property.entry.item

What is the best way to convert that to a key for an associative array?

$result['imported_data']['property']['entry']['item']

The string may be of any length, with any number of dots and contain an value:

people.arizona.phoenix.smith

I've tried the following without success:

//found a dot, means we are expecting output from a previous function if( preg_match('[.]',$value)) { //check for previous function output if(!is_null($result['import'])) { $chained_result_array = explode('.',$value); //make sure we have an array to work with if(is_array($chained_result_array)) { $array_key = ''; foreach($chained_result_array as $key) { $array_key .= '[\''.$key.'\']'; } } die(print_r(${result.'[\'import\']'.$array_key})); } }

I was thinking I could convert the string to a variable variable, but I get an array to string conversion error.

Bob van Luijt · Accepted Answer · 2015-11-30 23:23:41Z

2

You can explode the string into an array and loop through the array. (DEMO)

/** * This is a test array */ $testArray['property']['entry']['item'] = 'Hello World'; /** * This is the path */ $string = 'property.entry.item'; /** * This is the function */ $array = explode('.', $string); foreach($array as $i){ if(!isset($tmp)){ $tmp = &$testArray[$i]; } else { $tmp = $tmp[$i]; } } var_dump( $tmp ); // output = Hello World

edited Nov 30, 2015 at 23:23

answered Nov 30, 2015 at 23:15

Bob van Luijt

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9 Comments

sterling Over a year ago

I am not looking to get the values of the string, I am looking to use the values of the string as a key for another array. Does that make sense?

Steve Over a year ago

Snap, and a bit quicker than me, @sterling you are misreading his code - this does just what you want - see the live example in my answer for proof - this is essentially the same technique

Bob van Luijt Over a year ago

@sterling Check the updated answer, it's in a bit more detail now

Bob van Luijt Over a year ago

Made it a bit more cleaner by setting a pointer to $testArray

sterling Over a year ago

Thank you, I see now. I am trying to understand the implication of the reference variable. Also, how would you approach this if you had to prefix each final array with $result['import'] ?

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Steve · Accepted Answer · 2015-11-30 23:16:33Z

Split the string into parts, and itterate the array, accessing each element in turn:

function arrayDotNotation($array, $dotString){ foreach(explode('.', $dotString) as $section){ $array = $array[$section]; } return $array; } $array = ['one'=>['two'=>['three'=>'hello']]]; $string = 'one.two.three'; echo arrayDotNotation($array, $string); //outputs hello

Live example: http://codepad.viper-7.com/Vu8Hhy

slashingweapon · Accepted Answer · 2015-11-30 23:45:33Z

You should really check to see if keys exist before you reference them. Otherwise, you're going to spew a lot of warnings.

function getProp($array, $propname) { foreach(explode('.', $propname) as $node) { if(isset($array[$node])) $array = &$array[$node]; else return null; } return $array; }

Now you can do things like:

$x = array( 'name' => array( 'first' => 'Joe', 'last' => 'Bloe', ), 'age' => 27, 'employer' => array( 'current' => array( 'name' => 'Some Company', ) ) ); assert(getProp($x, 'age') == 27); assert(getProp($x, 'name.first') == 'Joe'); assert(getProp($x, 'employer.current.name') == 'Some Company'); assert(getProp($x, 'badthing') === NULL); assert(getProp($x, 'address.zip') === NULL);

Or, if you are only interested in the import section of the tree:

getProp($x['import'], 'some.path');

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