(PHP 7 >= 7.2.0)
imageresolution — Get or set the resolution of the image
imageresolution ( resource $image ) : mixed
imageresolution ( resource $image , int $res_x [, int $res_y = $res_x ] ) : mixed
imageresolution() allows to set and get the resolution of an image in DPI (dots per inch). If none of the optional parameters is given, the current resolution is returned as indexed array. If only res_x is given, the horizontal and vertical resolution are set to this value. If both optional parameters are given, the horizontal and vertical resolution are set to these values, respectively.
The resolution is only used as meta information when images are read from and written to formats supporting this kind of information (curently PNG and JPEG). It does not affect any drawing operations. The default resolution for new images is 96 DPI.
image
An image resource, returned by one of the image creation functions, such as imagecreatetruecolor().
res_x
The horizontal resolution in DPI.
res_y
The vertical resolution in DPI.
When used as getter (first signature), it returns an indexed array of the horizontal and vertical resolution on success, or false on failure. When used as setter (second signature), it returns true on success, or false on failure.
Example #1 Setting and getting the resolution of an image
<?php $im = imagecreatetruecolor(100, 100); imageresolution($im, 200); print_r(imageresolution($im)); imageresolution($im, 300, 72); print_r(imageresolution($im)); ?>
The above example will output:
Array
(
[0] => 200
[1] => 200
)
Array
(
[0] => 300
[1] => 72
)
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https://www.php.net/manual/en/function.imageresolution.php