imagegif

imagegif is a PHP function provided by the GD graphics library used to output or save a GIF image representation of a given image resource. It is commonly used in server-side image generation workflows to produce GIF images dynamically.

Signature and behavior: bool imagegif(resource $image, string $filename = null). If a filename is supplied, the function writes the GIF image to the specified file and returns true on success; if no filename is provided, the GIF data is sent to the output buffer (typically the browser) and false is returned on failure. When streaming to a browser, ensure the correct Content-Type header, such as Content-Type: image/gif.

Requirements and limitations: The GD extension must be compiled with GIF support. The $image resource is typically created with functions like imagecreatetruecolor or loaded from an existing image resource using imagecreatefromjpeg, imagecreatefrompng, etc. The output GIF is a single frame; GD's GIF encoder converts truecolor images to a 256-color palette, which may affect color fidelity. Animated GIFs are not produced by a single imagegif call; creating animations requires multiple frames or alternative libraries.

Other notes: Transparency can be preserved using imagecolortransparent; imagegif returns true on success, false on failure; The function is analogous to imagejpeg and imagepng for GIF output.

Example: $im = imagecreatetruecolor(100, 100); imagefill($im, 0, 0, imagecolorallocate($im, 255, 0, 0)); imagegif($im, 'redbox.gif');