The best method to store a PHP Array: json_encode vs serialize

Depends on your priorities.

If performance is you absolute driving characteristic, then by all means use the fastest one. Just make sure you have a full understanding of the differences before you make a choice:

• JSON converts UTF-8 characters to unicode escape sequences. serialize() does not.
• JSON will have no memory of what the object's original class was (they are always restored as instances of stdClass).
• You can't leverage __sleep() and __wakeup() with JSON
• Only public properties are serialized with JSON
• JSON is more portable

And there's probably a few other differences I can't think of at the moment.

A simple speed test to compare the two:

ini_set( 'display_errors', 1 );
error_reporting( E_ALL );

//  Make a bit, honkin test array
//  You may need to adjust this depth to avoid memory limit errors
$testArray = fillArray( 0, 5 );

//  Time json encoding
$start = microtime( true );
json_encode( $testArray );
$jsonTime = microtime( true ) - $start;
echo "JSON encoded in $jsonTime seconds<br>";

//  Time serialization
$start = microtime( true );
serialize( $testArray );
$serializeTime = microtime( true ) - $start;
echo "PHP serialized in $serializeTime seconds<br>";

//  Compare them
if ( $jsonTime < $serializeTime )
{
    echo "json_encode() was roughly " . number_format( ($serializeTime / $jsonTime - 1 ) * 100, 2 ) . "% faster than serialize()";
}
else if ( $serializeTime < $jsonTime )
{
    echo "serialize() was roughly " . number_format( ($jsonTime / $serializeTime - 1 ) * 100, 2 ) . "% faster than json_encode()";
} else {
    echo 'Unpossible!';
}

function fillArray( $depth, $max )
{
    static $seed;
    if ( is_null( $seed ) )
    {
        $seed = array( 'a', 2, 'c', 4, 'e', 6, 'g', 8, 'i', 10 );
    }
    if ( $depth < $max )
    {
        $node = array();
        foreach ( $seed as $key )
        {
            $node[$key] = fillArray( $depth + 1, $max );
        }
        return $node;
    }
    return 'empty';
}

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How to: Serialize Object to JSON

JSON-js - JSON in JavaScript.

To convert an object to a string, use JSON.stringify:

var json_text = JSON.stringify(your_object, null, 2);

To convert a string to JSON object, use JSON.parse:

var your_object = JSON.parse(json_text);

It was recently recommended by John Resig:

...PLEASE start migrating your JSON-using applications over to Crockford's json2.js. It is fully compatible with the ECMAScript 5 specification and gracefully degrades if a native (faster!) implementation exists.

In fact, I just landed a change in jQuery yesterday that utilizes the JSON.parse method if it exists, now that it has been completely specified.

I tend to trust what he says on JavaScript matters :)

Newer browsers support the JSON object natively. The current version of Crockford's JSON library will only define JSON.stringify and JSON.parse if they're not already defined, leaving any browser native implementation intact.

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