PHP basic syntax - conditional statement

Seven, conditional statement

1. if statement

if (condition) { 
  code to execute when the condition is true; 
}

2. if...else statement

if (condition) { 
  code to execute if condition is true; 
} else { 
  code to execute if condition is false; 
}

3. if...elseif....else statement

if (condition) { 
  code to execute if condition is true; 
} elseif (condition) { 
  code to execute if condition is true; 
} else { 
  code to execute if condition is false; 
}

4. switch statement

grammar:

switch (expression) 
{ 
case label1: 
  the code executed when expression = label1; 
  break;   
case label2: 
  the code executed when expression = label2; 
  break; 
default: 
  the code executed when the value of the expression is not equal to label1 and label2; 
}

principle:

1. perform an evaluation on an expression (usually a variable)
2. compares the value of the expression with the value of the case in the structure
3. If there is a match, the code associated with the case is executed
4. After the code is executed, the break statement prevents the code from jumping into the next case to continue execution
5. The default statement is used if no case is true