Reads image dimensions and type from bytes already held in a string.
What It Does
GD provides simple pixel-level operations; Imagick provides another image-processing API with distinct requirements. Untrusted data can be malformed; use a real decoder and resource limits for validation.
Requirements and Compatibility
PHP core. Sample images and fonts referred to by filename must be supplied locally. Use PHP 8 GdImage objects where applicable; optional decoders depend on the installed build.
Syntax, Inputs and Results
The arguments shown below are concrete values for this function; their types and ranges matter. The example checks return data rather than assuming that every operation succeeds.
Example 1: Basic Use
Call the function with a concrete input and inspect its result.
<?php
if (!is_file(__DIR__ . '/logo.png')) throw new RuntimeException('Provide the sample file /logo.png');
$result = getimagesizefromstring(file_get_contents(__DIR__ . '/logo.png'));
if ($result === false) throw new RuntimeException('Could not read image information');
print_r(array_slice($result, 0, 3));Example 2: Another Case
Change the inputs to observe the behavior on another case.
<?php
if (!is_file(__DIR__ . '/photo.jpg')) throw new RuntimeException('Provide the sample file /photo.jpg');
$result = getimagesizefromstring(file_get_contents(__DIR__ . '/photo.jpg'));
if ($result === false) throw new RuntimeException('Could not read image information');
print_r(array_slice($result, 0, 3));Practical Example
Use the result to create an output, validate a condition, or complete an image workflow.
<?php
$path = __DIR__ . '/photo.jpg';
if (!is_file($path)) throw new RuntimeException('Missing sample');
$info = getimagesizefromstring(file_get_contents(__DIR__ . '/logo.png'));
if ($info === false) throw new RuntimeException('Invalid metadata');
print_r($info);For production, apply the compatibility and edge-case limits described below.
Important Behavior and Edge Cases
Untrusted data can be malformed; use a real decoder and resource limits for validation.
Comparison with Related Functions and Tools
| Subject | Key difference |
|---|---|
| getimagesizefromstring() | GD provides simple pixel-level operations; Imagick provides another image-processing API with distinct requirements. |
Common Beginner Mistakes
| Mistake | Correct approach |
|---|---|
| Calling getimagesizefromstring() without its required input or supported extension | Check the extension, supply valid arguments, and handle false or exceptions according to the function. |
| Assuming getimagesizefromstring() guarantees a valid or safe image | Untrusted data can be malformed; use a real decoder and resource limits for validation. |
| Confusing the operation with a related API | GD provides simple pixel-level operations; Imagick provides another image-processing API with distinct requirements. |
Key Takeaways
- Reads image dimensions and type from bytes already held in a string.
- Untrusted data can be malformed; use a real decoder and resource limits for validation.
- Choose the companion API described in the comparison table when the job differs.
Use these examples as a starting point, then validate the result with the actual PHP build, dependencies and inputs used by your application.