PHP var_export vs var_dump for Complex Arrays

When debugging complex arrays in PHP, developers often rely on var_dump() and var_export() to inspect data structures. While both functions reveal the contents of an array, they serve different purposes: var_dump() is designed for detailed debugging by showing data types and values, whereas var_export() generates valid PHP code that can be copied, pasted, or evaluated. This article explains the key differences in their output structure, handling of special types, and ideal use cases.

1. Output Format and Type Information

The most immediate difference is how data types are represented.

• var_dump() provides verbose debugging information. For every element in the array, it explicitly outputs the data type and length (for strings).
• var_export() outputs representation that complies with PHP syntax. It does not display data types (like string or int) or string lengths; instead, it formats the data exactly as you would write it in a PHP script.

Example Comparison

Consider the following complex array:

$data = [
    "user" => "Alice",
    "active" => true,
    "scores" => [95, 87, 100],
    "null_value" => null
];

Output of var_dump($data):

array(4) {
  ["user"]=>
  string(5) "Alice"
  ["active"]=>
  bool(true)
  ["scores"]=>
  array(3) {
    [0]=>
    int(95)
    [1]=>
    int(87)
    [2]=>
    int(100)
  }
  ["null_value"]=>
  NULL
}

Output of var_export($data):

array (
  'user' => 'Alice',
  'active' => true,
  'scores' => 
  array (
    0 => 95,
    1 => 87,
    2 => 100,
  ),
  'null_value' => NULL,
)

2. Returning Output vs. Direct Echoing

By default, both functions output their results directly to the browser or command line. However, their behavior diverges when you need to capture this output into a variable.

• var_dump() always returns void. To capture its output, you must use output buffering (ob_start() and ob_get_clean()).
• var_export() accepts an optional second boolean parameter. Setting var_export($array, true) prevents direct output and instead returns the formatted string. This makes it ideal for logging or dynamically generating configuration files.

3. Handling of Objects and Special Types

When arrays contain complex types like objects, resources, or circular references, the two functions behave very differently.

• Objects: var_dump() outputs the internal properties of an object, including private and protected members. var_export() attempts to represent the object using the magic method __set_state(), which requires the target class to implement this method to be imported back into PHP successfully.
• Resources: var_dump() displays the resource type (e.g., resource(4) of type (stream)). var_export() cannot export resource variables and will output NULL instead.
• Circular References: If a complex array references itself, var_dump() detects the recursion and prints *RECURSION* to prevent an infinite loop. var_export() will trigger a fatal error or infinite recursion warning in older PHP versions because it cannot generate valid PHP code for self-referencing structures.

Summary: When to Use Which?

• Use var_dump() when you are actively debugging, need to inspect exact data types (distinguishing between 0, false, and null), or are dealing with circular references and system resources.
• Use var_export() when you want to generate configuration files, create test fixtures, log readable snapshots of arrays, or copy-paste array data directly back into your PHP code.