What are the most common PHP
filtering functions and techniques?

• Changing data type

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  • Force data type to (int)
  • Force data type to (float)
  • Useful for numeric values, IDs, etc.

• strip_tags()

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  • Removes HTML and Javascript tags
  • You can "whitelist" allowed tags

• str_replace()

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  • Search and replace
  • Use to remove undesired characters
  • Can use an array as an argument

• preg_replace()

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  • Use for intelligent search and replace
  • Use "u" modifier to support UTF-8
  • Performance considerations involved
  • Do not use in a lengthy loop