<?php
$arr = [
	'{
        "item1": "si",
        "item2": "no",
        "item3": [ 
            "{"
                "color": "azul",
                "tipo": "circulo"
            "}",
            "{"
                "color": "rojo",
                "tipo": "triangulo" 
            "}",
            "{"
                "color": "verde",
                "tipo": "cuadrado"
            "}"
        ]
    }'
];

function printArr($array){
    foreach($array as $key => $value){
        if (is_array($value)){
            echo $key . ': ' . printArr($value) . "\r\n";
        }
        else{
        	$object = json_decode($value);
        	if (!is_null($object)){
	        	echo $key . ': ' . "\r\n";
	        	foreach ($object as $k => $v){
	        		if (is_array($v)){
			            echo $k . ': ' . printArr($v) . "\r\n";
			        }
			        else{
	        			echo $k . ': ' . $v . "\r\n";	
			        }
	        	}
	        	echo "\r\n";
        	}
        	else{
        		echo $key . ': ' . $value . "\r\n";
        	}
        }
    }
}

printArr($arr);
?>