PHP Basics-1

echo "Hello", "AAAA";//output syntax, multiple strings can be output
print "World"; can be output, can only output a string with "." Splicing can be output, with "," Splicing direct error

Data type Int,double,float,string,char,datetime,bool
PHP Weak type language
Variable definition 1. No add type required; 2. Start with $
all variables in PHP start with the $ sign

Variable variable

$a = 5;
echo isset ($a);//Determine if the variable is defined; 0 or null in PHP means false

unset ($a);//Clear variable

Empty ($a);//Determine if the variable is an empty array

$b =& $a; & Take Address

$a = 5;
Var_dump ($a);//Output variable details

$b = (string) $a;//Type conversion
Var_dump ($b);

. is stitching (stitching string)

The "/" default string, so the integer in addition to the integer automatically converted to a string, the result appears decimal, need attention

"A +"

echo $a;//error suppressor, can block hint error

echo 5==5? " Male ":" NV "//Three mesh operator

PHP Basics-1