Flood-fills connected pixels of a matching color from a starting point.
What It Does
GD provides simple pixel-level operations; Imagick provides another image-processing API with distinct requirements. The fill depends on boundaries and color, not simply a rectangular area.
Requirements and Compatibility
GD extension. 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 (!extension_loaded('gd')) throw new RuntimeException('GD extension required');
$im = imagecreatetruecolor(160, 110);
$white = imagecolorallocate($im, 255, 255, 255);
imagefilledrectangle($im, 0, 0, 159, 109, $white);
$blue = imagecolorallocate($im, 34, 92, 166);
$ok = imagefill($im, 0, 0, $blue);
var_dump($ok);Example 2: Another Case
Change the inputs to observe the behavior on another case.
<?php
if (!extension_loaded('gd')) throw new RuntimeException('GD extension required');
$im = imagecreatetruecolor(160, 110);
$white = imagecolorallocate($im, 255, 255, 255);
imagefilledrectangle($im, 0, 0, 159, 109, $white);
$red = imagecolorallocate($im, 200, 65, 60);
$ok = imagefill($im, 45, 45, $red);
var_dump($ok);Practical Example
Use the result to create an output, validate a condition, or complete an image workflow.
<?php
if (!extension_loaded('gd')) throw new RuntimeException('GD extension required');
$im = imagecreatetruecolor(160, 110);
$white = imagecolorallocate($im, 255, 255, 255);
imagefilledrectangle($im, 0, 0, 159, 109, $white);
$red = imagecolorallocate($im, 200, 65, 60);
imagefill($im, 45, 45, $red);
if (!imagepng($im, __DIR__ . "/imagefill-demo.png")) throw new RuntimeException("Unable to save");For production, apply the compatibility and edge-case limits described below.
Important Behavior and Edge Cases
The fill depends on boundaries and color, not simply a rectangular area.
Comparison with Related Functions and Tools
| Subject | Key difference |
|---|---|
| imagefill() | GD provides simple pixel-level operations; Imagick provides another image-processing API with distinct requirements. |
Common Beginner Mistakes
| Mistake | Correct approach |
|---|---|
| Calling imagefill() without its required input or supported extension | Check the extension, supply valid arguments, and handle false or exceptions according to the function. |
| Assuming imagefill() guarantees a valid or safe image | The fill depends on boundaries and color, not simply a rectangular area. |
| Confusing the operation with a related API | GD provides simple pixel-level operations; Imagick provides another image-processing API with distinct requirements. |
Key Takeaways
- Flood-fills connected pixels of a matching color from a starting point.
- The fill depends on boundaries and color, not simply a rectangular area.
- 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.