How can I capture the result of var_dump to a string?
Use output buffering:
<?php
ob_start();
var_dump($someVar);
$result = ob_get_clean();
?>
Try var_export
You may want to check out var_export
— while it doesn't provide the same output as var_dump
it does provide a second $return
parameter which will cause it to return its output rather than print it:
$debug = var_export($my_var, true);
Why?
I prefer this one-liner to using ob_start
and ob_get_clean()
. I also find that the output is a little easier to read, since it's just PHP code.
The difference between var_dump
and var_export
is that var_export
returns a "parsable string representation of a variable" while var_dump
simply dumps information about a variable. What this means in practice is that var_export
gives you valid PHP code (but may not give you quite as much information about the variable, especially if you're working with resources).
Demo:
$demo = array(
"bool" => false,
"int" => 1,
"float" => 3.14,
"string" => "hello world",
"array" => array(),
"object" => new stdClass(),
"resource" => tmpfile(),
"null" => null,
);
// var_export -- nice, one-liner
$debug_export = var_export($demo, true);
// var_dump
ob_start();
var_dump($demo);
$debug_dump = ob_get_clean();
// print_r -- included for completeness, though not recommended
$debug_printr = print_r($demo, true);
The difference in output:
var_export ($debug_export
in above example):
array (
'bool' => false,
'int' => 1,
'float' => 3.1400000000000001,
'string' => 'hello world',
'array' =>
array (
),
'object' =>
stdClass::__set_state(array(
)),
'resource' => NULL, // Note that this resource pointer is now NULL
'null' => NULL,
)
var_dump ($debug_dump
in above example):
array(8) {
["bool"]=>
bool(false)
["int"]=>
int(1)
["float"]=>
float(3.14)
["string"]=>
string(11) "hello world"
["array"]=>
array(0) {
}
["object"]=>
object(stdClass)#1 (0) {
}
["resource"]=>
resource(4) of type (stream)
["null"]=>
NULL
}
print_r ($debug_printr
in above example):
Array
(
[bool] =>
[int] => 1
[float] => 3.14
[string] => hello world
[array] => Array
(
)
[object] => stdClass Object
(
)
[resource] => Resource id #4
[null] =>
)
Caveat: var_export
does not handle circular references
If you're trying to dump a variable with circular references, calling var_export
will result in a PHP warning:
$circular = array();
$circular['self'] =& $circular;
var_export($circular);
Results in:
Warning: var_export does not handle circular references in example.php on line 3
array (
'self' =>
array (
'self' => NULL,
),
)
Both var_dump
and print_r
, on the other hand, will output the string *RECURSION*
when encountering circular references.