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Dumping Variables — Zend Framework 2 2.3.9 documentation
The static method Zend\Debug\Debug::dump() prints or returns information about an expression. This simple technique of debugging is common because it is easy to use in an ad hoc fashion and requires no initialization, special tools, or debugging environment.
Zend\Debug\Debug::dump($var, $label = null, $echo = true);
The $var argument specifies the expression or variable about which the Zend\Debug\Debug::dump() method outputs information.
The $label argument is a string to be prepended to the output of Zend\Debug\Debug::dump(). It may be useful, for example, to use labels if you are dumping information about multiple variables on a given screen.
The boolean $echo argument specifies whether the output of Zend\Debug\Debug::dump() is echoed or not. If TRUE, the output is echoed. Regardless of the value of the $echo argument, the return value of this method contains the output.
It may be helpful to understand that Zend\Debug\Debug::dump() method wraps the PHP function var_dump(). If the output stream is detected as a web presentation, the output of var_dump() is escaped using htmlspecialchars() and wrapped with (X)HTML <pre> tags.
Debugging with ZendLog
Using Zend\Debug\Debug::dump() is best for ad hoc debugging during software development. You can add code to dump a variable and then remove the code very quickly.
Also consider the ZendLog component when writing more permanent debugging code. For example, you can use the DEBUG log level and the stream log writer to output the string returned by Zend\Debug\Debug::dump().