Php basics 2: common functions

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• Syntax
• Syntax

Define ()A function defines a constant.

Constants are similar to variables, except that:

define(name,value,case_insensitive)

Parameters	Description
Name	Required. Specifies the name of a constant.
Value	Required. Specifies the value of a constant.
Case_insensitive	Required. Specifies whether the constant name is case sensitive. If it is set to true, it is not case sensitive. The default value is false (case sensitive ).

 

Isset-Check whether the variables are set.

Bool Isset(Mixed $ Var[, Mixed $ Var[, $...])

IfVarIf yes, returnTRUEOtherwise, returnFALSE. If you have used unset ()
After a variable is released, it will no longer beIsset (). If you useIsset ()TestNULLWill returnFALSE. Note thatNULL
Byte ("\ 0") Is not equivalent to PHP'sNULLConstant.

 

Unpack ()
The function unpacks data from a binary string.

Syntax

unpack(format,data)

Parameters	Description
Format	Required. Specifies the format used to unpack data.
Data	Optional. Specifies the binary data to be unwrapped.

Fread
Fread-read files (which can be safely used for binary files)
StringFread(Int$ Handle, Int$ Length)
Fread ()Slave file pointerHandleRead MostLengthBytes. This function can be used upLengthNumber of bytes, or when the EOF is reached, or (for network streams) when a package is available, or (after opening the user space Stream) when 8192 bytes have been read, the system stops reading files.
Returns the read string. If an error occursFALSE.
 
Str_repeat ()
The number of times the string is repeated.
Syntax
str_repeat(string,repeat)
 
 

  
  
 
   
 
    
Parameters
 
    
Description
 
   
 
   
 
    
String
 
    
Required. Specifies the string to be repeated.
 
   
 
   
 
    
Repeat
 
    
Required. Specifies the number of times the string will be repeated. Must be greater than or equal to 0.