PHP Variable variables Examples
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Variable variables in PHP allow the name of a variable to be dynamically set and accessed using the value of another variable. They are useful for situations where variable names need to be dynamically generated, such as when uniquely identifying employees or students with IDs. Examples shown include outputting a name based on an ID variable, generating variables from an array, and simulating Excel's indirect() function to create dependent drop-down lists in a form. Variable variables can reduce code, provide a central sanitization point for external inputs, and make variable names easier to modify.
PHP Variable variables Examples
- 1. PHP Variable Variables Examples Abdul Rahman Sherzad Computer Science Lecturer Herat University, Afghanistan
- 2. Definition ■ Variable variables take 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
- 3. Example 1 ■ Employees share 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
- 4. Example 2 ■ It is 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
- 5. Example 2 - Array ■ This is another method to accomplish Example 2 in the previous slide using array. 5
- 6. Example 3 ■ Variable variables 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
- 7. 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
- 8. Example 4 ■ Use variable 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
- 9. Example 5 ■ PHP variable 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
- 10. Example 5 - complete 10
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