{"id":786,"date":"2017-03-18T15:00:01","date_gmt":"2017-03-18T09:30:01","guid":{"rendered":"https:\/\/www.wikitechy.com\/technology\/?p=786"},"modified":"2017-03-29T15:00:10","modified_gmt":"2017-03-29T09:30:10","slug":"can-capture-result-var_dump-string-2","status":"publish","type":"post","link":"https:\/\/www.wikitechy.com\/technology\/can-capture-result-var_dump-string-2\/","title":{"rendered":"PHP – How can we capture the result of var_dump to a string"},"content":{"rendered":"

What is var_dump?<\/strong><\/p>\n

The\u00a0var_dump manual page [ http:\/\/php.net\/var_dump<\/a> ]\u00a0states that var_dump displays structured information about one or more expressions that includes its type and value.<\/p>\n

Arrays and objects are explored recursively with values indented to show structure.<\/p>\n

Description<\/strong> :<\/p>\n

Php Code<\/span> <\/div> 
void var_dump ( mixed $expression [, mixed $... ] )<\/code><\/pre> <\/div>\n[ad type=”banner”]\n
This function displays structured information about one or more expressions that includes its type and value.<\/p>\n
Arrays and objects are explored recursively with values indented to show structure.<\/p>\n
All public, private and protected properties of objects will be returned in the output unless the object implements a\u00a0__debugInfo()
\n[ http:\/\/us3.php.net\/manual\/en\/language.oop5.magic.php#language.oop5.magic.debuginfo ]\u00a0<\/strong>method (implemented in PHP 5.6.0).<\/p>\n
Example #1<\/strong><\/p>\n
var_dump() example:<\/strong><\/p>\n
 
 Php Code<\/span> <\/div> 
<?php$b = 3.1;$c = true;var_dump($b, $c);?><\/code><\/pre> <\/div>\n
The above example will output:<\/strong><\/p>\n
 
 Php Code<\/span> <\/div> 
float(3.1)bool(true)<\/code><\/pre> <\/div>\n
The problem is that var_dump outputs its result directly to the browser, how can you capture its output in a string variable? read on…<\/p>\n
Using output control functions for the solution:<\/strong><\/p>\n
Output control functions can be used to capture and redirect the standard output. For more details, read the\u00a0PHP manual on output control functions
\n[ http:\/\/php.net\/manual\/en\/ref.outcontrol.php ], <\/strong>of course.<\/p>\n
 
 Php Code<\/span> <\/div> 
<?phpfunction varDumpToString($var) {    ob_start();    var_dump($var);    $result = ob_get_clean();    return $result;}\/\/\/\/Example usage:\/\/    $data = array('first', 'second', 'third');\/\/    $result = varDumpToString($data);\/\/<\/code><\/pre> <\/div>\n[ad type=”banner”]\n
Sample code:<\/strong><\/p>\n
Use output buffering:<\/strong><\/p>\n
 
 Php Code<\/span> <\/div> 
<?phpob_start();var_dump($someVar);$result = ob_get_clean();?><\/code><\/pre> <\/div>\n
A smart alternative to PHP\u2019s \u201cvar_dump\u201d function<\/strong><\/p>\n
The \u201cvar_debug\u201d function is a smart alternative to PHP\u2019s \u201cvar_dump\u201d function, which limits the output and prints the file path and line of the invocation.<\/p>\n
File path and line of invocation<\/strong><\/p>\n
The \u201cvar_debug\u201d function outputs the file path and line number of the invocation. So even when your \u201cvar_dump\u201d calls all say the same you can still see what happened. To accomplish this, it uses the PHP \u201cdebug_backtrace\u201d function.<\/p>\n
It sets the \u201cDEBUG_BACKTRACE_IGNORE_ARGS\u201d option to reduce memory usage. From the produced backtrace, it gets the first element that holds a file path and line number and it adds that to the start of the output.<\/p>\n
Limit the output:<\/strong><\/p>\n
The \u201cvar_debug\u201d function limits the output with the following default rules:<\/p>\n
Only the first 100 characters of each string are logged (full length is shown)<\/p>\n
Only the first 25 elements of an array are logged (full length is shown)<\/p>\n
Only the first 10 levels of nested objects\/arrays are logged<\/p>\n
These three limits can be set using three optional parameters in the above order. Hence, calling \u201cvar_debug($variable)\u201d is equal to calling \u201cvar_debug($variable,100,25,10)\u201d.<\/p>\n
Modifications:<\/strong><\/p>\n
If you would like the function to echo HTML-printable output, you can replace the last line that says \u201cecho $string;\u201d with the following:<\/strong><\/p>\n
 
 Php Code<\/span> <\/div> 
echo nl2br(str_replace(' ',' ',htmlentities($string)));<\/code><\/pre> <\/div>\n
Replace \u201cecho $string;\u201d with \u201creturn $string;\u201d if you want to use the output for logging purposes in some other function.<\/p>\n
var_export<\/strong><\/p>\n
You may want to check out var_export \u2014 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:<\/strong><\/p>\n
 
 Php Code<\/span> <\/div> 
$debug = var_export($my_var, true);<\/code><\/pre> <\/div>\n[ad type=”banner”]\n
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.<\/p>\n
What this means in practice is that var_export gives you valid PHP code.<\/p>\n
Demo:<\/strong><\/p>\n
 
 Php Code<\/span> <\/div> 
$demo = array(    "bool" => false,    "int" => 1,    "float" => 3.14,    "string" => "hello world",    "array" => array(),    "object" => new stdClass(),    "resource" => tmpfile(),    "null" => null,);\/\/ var_export -- nice, one-liner$debug_export = var_export($demo, true);\/\/ var_dumpob_start();var_dump($demo);$debug_dump = ob_get_clean();\/\/ print_r -- included for completeness, though not recommended$debug_printr = print_r($demo, true);<\/code><\/pre> <\/div>\n
The difference in output:<\/strong><\/p>\n
var_export ($debug_export in above example)<\/strong><\/p>\n
 
 Php Code<\/span> <\/div> 
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,):<\/code><\/pre> <\/div>\n
var_dump ($debug_dump in above example)<\/strong><\/p>\n
 
 Php Code<\/span> <\/div> 
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}<\/code><\/pre> <\/div>\n
print_r ($debug_printr in above example):<\/strong><\/p>\n
 
 Php Code<\/span> <\/div> 
Array(    [bool] =>     [int] => 1    [float] => 3.14    [string] => hello world    [array] => Array        (        )    [object] => stdClass Object        (        )    [resource] => Resource id #4    [null] => )<\/code><\/pre> <\/div>\n
Caveat: var_export does not handle circular references<\/strong><\/p>\n
If you’re trying to dump a variable with circular references, calling var_export will result in a PHP warning:<\/strong><\/p>\n
 
 Php Code<\/span> <\/div> 
$circular = array(); $circular['self'] =& $circular; var_export($circular);<\/code><\/pre> <\/div>\n
Results in:<\/strong><\/p>\n
 
 Php Code<\/span> <\/div> 
Warning: var_export does not handle circular references in example.php on line 3 array (   'self' =>    array (     'self' => NULL,   ), )<\/code><\/pre> <\/div>\n[ad type=”banner”]\n
Both var_dump and print_r, on the other hand, will output the string *RECURSION* when encountering circular references.<\/p>\n","protected":false},"excerpt":{"rendered":"
What is var_dump? The\u00a0var_dump manual page [ http:\/\/php.net\/var_dump ]\u00a0states that var_dump displays structured information about one or more expressions that includes its type and value. Arrays and objects are explored recursively with values indented to show structure. Description : [ad type=”banner”] This function displays structured information about one or more expressions that includes its type […]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[25],"tags":[1428,1436,1432,1435,1431,1434,1426,1429,1433,1430,1427],"class_list":["post-786","post","type-post","status-publish","format-standard","hentry","category-php","tag-how-to-put-php-var_dump-in-a-variable","tag-how-to-remove-a-particular-element-from-an-array-in-javascript","tag-php-var_dump-all-variables","tag-php-var_dump-to-error-log","tag-php-var_export","tag-print_r-to-string","tag-the-definitive-guide-to-phps-isset-and-empty","tag-var_dump-vs-print_r","tag-var_dump_post","tag-var_export-to-file","tag-writing-to-the-php-error_log-with-var_dump-print_r"],"_links":{"self":[{"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/posts\/786","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/comments?post=786"}],"version-history":[{"count":0,"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/posts\/786\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/media?parent=786"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/categories?post=786"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/tags?post=786"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}