Annotated symbols: // one-line notes Multi-line comment Use of quotation marks “Single quote, simple string, brought in without any processing; "" double quotes,php dynamic processing and then output,1 generally used to handle the $variable. Boolean variable: One is true which is true; The other is false, which is fake Common variables: string string (Numbers, Chinese characters, etc.) integer integers (1, 2, 3, 4, 5, 0, -1, -2, etc.) double floating point number array array object object The available methods are gettype($mix) and settype($mix,$typename);
Common symbol escape:
\ “double quotation marks \ \ the backslash \ n newline \ r back to the beginning of a line \t horizontal tabulation Operation symbol: Plus plus minus minus * multiplication/division Take the remainder of % ++ add 1 Concatenate two strings Assignment operation: = substitute the value on the right into the value on the left += add the right-hand side to the left-hand side -= subtract the right-hand side from the left-hand side *= multiply the left-hand side by the right-hand side /= divide the left-hand side by the right-hand side .= add the right string to the left Operation: & Bitwise and | or by location ^ by bit or (xor) < < We’re going to move 1 bit to the left > > I’m going to move 1 bit to the right ~ take a complement Logical operation: < Less than > Is greater than < Is less than or equal to > Is greater than or equal to ! = is not equal to & & with | | or! non Other operation symbols $variable symbol & Variable alias @ does not display error message (added before function) - > Object’s methods or properties = > The element values of the array ? : 3 meta operator
Common basic methods:
1.PHP converts strings to case!
strtolower (); Convert characters to lowercase strtoupper (); Convert characters to uppercase
2.PHP encrypted string
Non-reducible: md5(); sha1(); Can restore: base64_encode(); base64_decode();
3. About quotation marks
1. Single quotes are output as is 2. Double quotation marks are content interpretation for output 3. Anti-single quotes (small quotes) are the execution of a system command, such as’ dir ’. Often used in table names, field names above. 4. ”\” ACTS on the translated characters, such as “\n” for line feed.
4. Functions :htmlspecialchars() and htmlentities() This function converts a special character to the string format of HTML ( & . ; ). One of the most common situations is probably the message board for customer messages.
& (and) turn into & amp; “(double quotation marks) & quot; < PI is less than PI & lt; > (greater than) into & gt; (blank) into & nbsp;
5. Batch output HTML content!
echo < < < EOT HTML output content… // comments are still output here! EOT;
print < < < EOT HTML output content… // comments are still output here! EOT; (note: “{variable}” is used for internal containing variables.)
6. Determine whether the file exists and output the content file_exists ()
< ?php $FileName=“File.TXT”; if (file_exists($FileName)){ echo ” < pre > “.file_get_contents($FileName).” < /pre > ”; }else { echo”no”; } ? >
7. Delete variables to free memory unset();
unset($var); unset($var,$var1);
8.is_numeric; Test whether the variable is a number;
9.is_int; Test whether the variable is an integer;
10.is_null; Test whether the variable is NULL;
11.is_string Detects whether the variable is a string
12.is_real; is_float (alias)
13.isset Detects whether a variable is defined
14.is_bool Test whether the variable is Boolean
15.is_array Detects whether the variable is an array
16.is_object Detects whether a variable is an object
The 17.substr() function returns part 1 of the string.
substr (String,Start,SelectNum)
echo substr('abcdef', 1); // bcdef
echo substr('abcdef', 1, 3); // bcd
echo substr('abcdef', 0, 4); // abcd
echo substr('abcdef', 0, 8); // abcdef
echo substr('abcdef', -1, 1); // f18.nb2br() changes the escaped newline to html < br / >
echo nl2br("foo isn't\n bar");