PHP imagejpeg() Function: Usage and Examples

Saves or streams a GD image as lossy JPEG.

What It Does

imagepng() is lossless and supports alpha; JPEG is lossy and has no alpha; AVIF needs codec support. Quality uses 0–100; JPEG cannot preserve transparent alpha pixels.

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, $white);
if (!imagejpeg($im, __DIR__ . '/out.jpg', 85)) throw new RuntimeException('Encoding failed');
echo 'File written';

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, $white);
if (!imagejpeg($im, __DIR__ . '/preview.jpg', 65)) throw new RuntimeException('Encoding failed');
echo 'File written';

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);
ob_start();
$ok = imagejpeg($im, null, 78);
$bytes = ob_get_clean();
if (!$ok || !is_string($bytes) || $bytes === "") throw new RuntimeException("Image encoder failed");
echo strlen($bytes), " encoded bytes";

For production, apply the compatibility and edge-case limits described below.

Important Behavior and Edge Cases

Quality uses 0–100; JPEG cannot preserve transparent alpha pixels.

Comparison with Related Functions and Tools

Common Beginner Mistakes

Key Takeaways

• Saves or streams a GD image as lossy JPEG.
• Quality uses 0–100; JPEG cannot preserve transparent alpha pixels.
• 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.