- Signed URLs
- Srcset Generation
Define the following requirement in your
And include the global
Just copy the files to your project, and include the
src/autoload.php file. We recommend using Composer if at all possible.
To begin creating imgix URLs programmatically, add the php files to your project (an example autoloader is also provided). The URL builder can be reused to create URLs for any images on the domains it is provided.
HTTPS support is available by default. However, if you need HTTP support, call
setUseHttps on the builder:
To produce a signed URL, you must enable secure URLs on your source and then provide your signature key to the URL builder.
The imgix-php package allows for generation of custom srcset attributes, which can be invoked through the
createSrcSet method. By default, the generated srcset will allow for responsive size switching by building a list of image-width mappings.
The above will produce the following srcset attribute value which can then be served to the client:
In cases where enough information is provided about an image's dimensions,
createSrcSet will instead build a srcset that will allow for an image to be served at different resolutions. The parameters taken into consideration when determining if an image is fixed-width are
createSrcSet with either a width or height provided, a different srcset will be generated for a fixed-width image instead.
Will produce the following attribute value:
For more information to better understand srcset, we highly recommend Eric Portis' "Srcset and sizes" article which goes into depth about the subject.
This library will automatically append a variable
q parameter mapped to each
dpr parameter when generating a fixed-width image srcset. This technique is commonly used to compensate for the increased file size of high-DPR images.
Since high-DPR images are displayed at a higher pixel density on devices, image quality can be lowered to reduce overall file size––without sacrificing perceived visual quality. For more information and examples of this technique in action, see this blog post.
This behavior will respect any overriding
q value passed in as a parameter. Additionally, it can be disabled altogether by passing
$disableVariableQuality = true to
This behavior specifically occurs when a fixed-width image is rendered, for example:
The above will generate a srcset with the following
In situations where specific widths are desired when generating
srcset pairs, a user can specify them by passing an array of positive integers as
'widths' within the
Note: in situations where a
srcset is being rendered as a fixed-width srcset, any custom
widths passed in will be ignored.
Additionally, if both
widths and a width
tolerance are passed to the
createSrcSet method, the custom widths list will take precedence.
In certain circumstances, you may want to limit the minimum or maximum value of the non-fixed
srcset generated by the
createSrcSet method. To do this, you can specify the widths at which a srcset should
Formatted version of the above srcset attribute:
tolerance dictates the maximum
tolerated difference between an image's downloaded size and its rendered size.
For example, setting this value to
10 means that an image will not render more than 10% larger or smaller than its native size. In practice, the image URLs generated for a width-based srcset attribute will grow by twice this rate.
A lower tolerance means images will render closer to their native size (thereby increasing perceived image quality), but a large srcset list will be generated and consequently users may experience lower rates of cache-hit for pre-rendered images on your site.
By default, srcset width
tolerance is set to 8 percent, which we consider to be the ideal rate for maximizing cache hits without sacrificing visual quality. Users can specify their own width tolerance by providing a positive scalar value as width
In this case, the width
tolerance is set to 20 percent, which will be reflected in the difference between subsequent widths in a srcset pair:
For security and diagnostic purposes, we sign all requests with the language and version of library used to generate the URL.
This can be disabled by setting
False like so:
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