php中var_dump()函数的详解说明

$a = "alsdflasdf;a";
$b = var_dump($a);
echo "
";
//var_dump($c);
$d=var_dump($c);
echo "
";
echo $a;
echo "
";
echo $b;
echo "
";
输出：
string(12) "alsdflasdf;a"
NULL
alsdflasdf;a

$a = array (1, 2, array ("a", "b", "c"));

var_dump ($a);

/* 输出：

array(3) {

  [0]=>

  int(1)

  [1]=>

  int(2)

  [2]=>

  array(3) {

    [0]=>

    string(1) "a"

    [1]=>

    string(1) "b"

    [2]=>

    string(1) "c"

  }

}
*/
$b = 3.1;

$c = TRUE;

var_dump($b,$c);
/* 输出：

float(3.1)

bool(true)
*/

?>

set_time_limit(50);
$a = array(1,2,3);
$b = array('a'=>1, 'b'=>2, 'c'=>3);
$c = array('a'=>array(1,2,3), 'b'=>array(4,5,6));

$time1 = microtime(true);

$times = 1000000; #10w

for($i=1; $i<=$times; $i++){
 $A = var_export($a, true);
}

$time2 = microtime(true);

for($i=1; $i<=$times; $i++){
 $B = var_export($b, true);
}

$time3 = microtime(true);

for($i=1; $i<=$times; $i++){
 $C = var_export($c, true);
}

$time4 = microtime(true);

for($i=1; $i<=$times; $i++){
 $X = serialize($a);
}

$time5 = microtime(true);

for($i=1; $i<=$times; $i++){
 $Y = serialize($b);
}

$time6 = microtime(true);

for($i=1; $i<=$times; $i++){
 $Z = serialize($c);
}

$time7 = microtime(true);

for($i=1; $i<=$times; $i++){
 $O = unserialize($X);
}

$time8 = microtime(true);

for($i=1; $i<=$times; $i++){
 $P = unserialize($Y);
}

$time9 = microtime(true);

for($i=1; $i<=$times; $i++){
 $Q = unserialize($Z);
}
$time10 = microtime(true);

$var_export_time['a'] = $time2 - $time1;
$var_export_time['b'] = $time3 - $time2;
$var_export_time['c'] = $time4 - $time3;

$serialize_time['a'] = $time5 - $time4;
$serialize_time['b'] = $time6 - $time5;
$serialize_time['c'] = $time7 - $time6;

$unserialize_time['a'] = $time8 - $time7;
$unserialize_time['b'] = $time9 - $time8;
$unserialize_time['c'] = $time10 - $time9;
print_r($var_export_time);
print_r($serialize_time);
print_r($unserialize_time);
?>
output:
Array(    [a] => 3.3401498794556    [b] => 5.1394801139832    [c] => 8.8483898639679)Array(    [a] => 1.6063709259033    [b] => 1.7033960819244    [c] => 3.4534389972687)Array(    [a] => 1.6037359237671    [b] => 1.817803144455    [c] => 3.7992968559265)