PHP Variable variables Examples

PHP Variable variables Examples

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  PHP Variable Variables Examples AbdulRahman Sherzad Computer Science Lecturer Herat University, Afghanistan
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  Definition ■ Variable variablestake the value of one variable, and treat that as the name of another variable. ■ Variable variables are just variables whose names can be programmatically set and accessed. Hence, they are also called dynamic variable names. 2
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  Example 1 ■ Employeesshare similar name. Hence, all employees are given a unique identifier (ID, aka code) by organizations. This unique code is important for the organizations to distinguish their employees. ■ Likewise, educational institutions assign a unique code for their students. ■ This unique code is very important for the system, but it alone is not very informative in reports. ■ Variable variables can be used in such situations to cover both. Following code creates a variable called $S20120, and outputs the string "Abdul Rahman Sherzad". 3
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  Example 2 ■ Itis also possible to use value of a variable/literal value as part of variable variables names. ■ Of course, there are many other easy ways to accomplish the functionality of this program. But this is to explain variable variables concept through examples. 4
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  Example 2 -Array ■ This is another method to accomplish Example 2 in the previous slide using array. 5
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  Example 3 ■ Variablevariables can be used to dynamically generate variables from an associative array. ■ The PHP extract() built-in function also takes an associative array and treats the keys as variable names and the values as variable values, (see next slide). ■ This example is to describe and demonstrate the variable variables applications, not reinventing the wheel. 6
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  Example 3 -Extract ■ The PHP extract() function takes an associative array and treats the keys as variable names and the values as variable values. ■ The extract() has useful functionality such as to prevent variables that already exist. ■ Also it enables one to group the variables by using prefixes too. 7
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  Example 4 ■ Usevariable variables to convert POST variables to local variables, as illustrated in the example. ■ This technique has several benefits. – Lines of code are reduced, – Central place to clean and sanitize all external input, – Easy change and modification of variable names. 8
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  Example 5 ■ PHPvariable variables can simulate Microsoft Excel’s indirect() function to create dependent drop-down lists. ■ In this example, it is shown how to create dependent drop-down lists, using variable variables names. ■ Of course, there are better ways to accomplish creating dependent drop- down lists. In this presentation, the purpose is to show the application and example of variable variables in PHP. 9
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  Example 5 -complete 10
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