The eval() function evaluates a string as PHP code.Syntaxeval(code)Parameterscode − The PHP code to be evaluated.ReturnThe eval() function returns null unless a return statement is called in the code string. Then the value passed to return is returned. if there is a parse error in the code string, eval() returns false.Example Live DemoOutputThe following is the output.This is $one $two! This is Demo text!

The die() function prints a message and exits the current script.Syntaxdie(msg)Parametersmsg − The message to write before exiting the script.ReturnThe die() function returns nothing.Example

The defined() function in PHP checks that constant exists or not.Syntaxdefined(name)Parametersname− The name of constant.ReturnThe defined() function returns true if the constant exists otherwise false.ExampleThe following is an example that checks whether a constant exist. Live DemoOutputThe following is the output.1

The define() function defines a constant.Syntaxdefine(const_name,value,case_insensitive)Parametersconst_name − The name of the constant.value − The value of the constant.case_insensitive − The constant name should be case-insensitive.ReturnThe define() function returns true on success or false on failure.ExampleThe following is an example that defines a constant. Live DemoOuptutThe following is the output.This is it!

The constant() function returns the value of a constant.Syntaxconstant(const)Parametersconst − The name of the constant to checkReturnThe constant() function returns the value of a constant and NULL if the constant is not defined.ExampleThe following is an example that defines a constant. Live DemoOutputThe following is the output.This is it!

The FILTER_CALLBACK constant calls a user defined function to filter the value.ReturnThe FILTER_CALLBACK constant does not return anything.ExampleThe following is an example that converts the case of a string. Here, existing function in PHP is taken. Live DemoOutputThe following is the output.demo text!

The FILTER_SANITIZE_URL constant removes all illegal URL characters from a string. It allows the following −$-_.+!*'(),{}|\^~[]`">

The FILTER_SANITIZE_STRIPPED constant encodes or strips unwanted characters.Options and FlagsFILTER_FLAG_NO_ENCODE_QUOTES − This flag does not encode quotesFILTER_FLAG_STRIP_LOW − Strips characters with ASCII value below 32FILTER_FLAG_STRIP_HIGH − Strips characters with ASCII value above 32FILTER_FLAG_ENCODE_LOW − Encodes characters with ASCII value below 32FILTER_FLAG_ENCODE_HIGH − Encodes characters with ASCII value above 32FILTER_FLAG_ENCODE_AMP − Encodes the & character to &ReturnThe FILTER_SANITIZE_STRIPPED constant does not return anything.Example Live DemoOutputThe following is the output.string(10) "Demo!text!"

For swapping characters of a string in Java we can use string builder which is mutable so we need not to take care of new object creation during swapping. In this we would create a method which swap characters of string based on location of swapping characters.This method will take location of swapping characters as its parameters.First store both characters need to be swapped and using set character method of string builder swap the targeted characters. Example Live Demo public class SwapCharacters { public static void main(String[] args) { ... Read More

The FILTER_SANITIZE_STRING constant deletes tags and encodes special characters from a string.FlagsFILTER_FLAG_NO_ENCODE_QUOTES − Do not encode quotesFILTER_FLAG_STRIP_LOW − Removes characters with ASCII value less than 32FILTER_FLAG_STRIP_HIGH − Removes characters with ASCII value greater than 127FILTER_FLAG_ENCODE_LOW − Encodes characters with ASCII value less than 32FILTER_FLAG_ENCODE_HIGH − Encodes characters with ASCII value greater than 127FILTER_FLAG_ENCODE_AMP − Encodes the "&" character to &ReturnThe FILTER_SANITIZE_STRING constant does not return anything.Example Live DemoOutputThe following is the output.Demo!