Learning Basic Logic In PHP

2026-10-18

Exercise 1

Display the letter grade based on the Nilai (Score) variable. The conditions we will use are as shown in the table below.

85-100: A
75-84: B
60-74: C
50-59: D
0-49: E

The following code is the PHP implementation of the problem above:

<?php
$nilai = (float) $_POST["q"];

if ($nilai > 100) {
    $rank = "???";
} elseif ($nilai >= 85) {
    $rank = "A";
} elseif ($nilai >= 75) {
    $rank = "B";
} elseif ($nilai >= 60) {
    $rank = "C";
} elseif ($nilai >= 50) {
    $rank = "D";
} elseif ($nilai < 50) {
    $rank = "E";
}
?>

Program Objective: To determine and classify a letter grade based on numeric score input according to a predefined range.

Input Retrieval: The code receives input via the HTTP POST method with the parameter “q”, which is then converted into a decimal data type (float) and stored in the $nilai variable.

Logical Structure (If-Elseif):

The program uses sequential branching to match the score range with the guideline table:
Invalid Value Handling: If $nilai is more than 100, the $rank variable is assigned the value “???”.
Grade A: If $nilai is greater than or equal to 85 (representing the 85-100 range), $rank becomes “A”.
Grade B: If $nilai is greater than or equal to 75 (representing the 75-84 range), $rank becomes “B”.
Grade C: If $nilai is greater than or equal to 60 (representing the 60-74 range), $rank becomes “C”.
Grade D: If $nilai is greater than or equal to 50 (representing the 50-59 range), $rank becomes “D”.
Grade E: If $nilai is less than 50 (representing the 0-49 range), $rank becomes “E”.

Output: The final result of this branching process is the assignment of a value to the $rank variable, which is ready to be displayed to the user.

Exercise 2

Display the IQ Percentage of the world population based on the table below.

0-29 = Idiot
30-40 = Mental Retardation
50-69 = Very Low IQ
70-79 = Moron
80-89 = Slow
90-109 = Average
110-119 = Normal Bright
120-129 = Smart
130-139 = Very Smart (Superior)
140+ = Genius
The following code is the PHP implementation of the problem above:

<?php
$iq = (float) $_POST["q"];

if ($iq >= 140) {
    $keterangan = "Genius";
} elseif ($iq >= 130) {
    $keterangan = "Very Smart (Superior)";
} elseif ($iq >= 120) {
    $keterangan = "Smart";
} elseif ($iq >= 110) {
    $keterangan = "Normal Bright";
} elseif ($iq >= 90) {
    $keterangan = "Average";
} elseif ($iq >= 80) {
    $keterangan = "Slow";
} elseif ($iq >= 70) {
    $keterangan = "Moron";
} elseif ($iq >= 50) {
    $keterangan = "Very Low IQ";
} elseif ($iq >= 30) {
    $keterangan = "Mental Retardation";
} elseif ($iq >= 0) {
    $keterangan = "Idiot";
} else {
    $keterangan = "Invalid value";
}
?>

Program Objective: To determine and display the description for a specific IQ score based on the guideline table of world population IQ percentages.

Input Retrieval: The program receives input values from a form via the POST method using the parameter “q”. This value is then converted into a decimal data type (float) and stored in the $iq variable.

Logical Structure (If-Elseif): The program uses a series of conditional branches from the highest score range to the lowest to align the logic with the table:

140+: If $iq is greater than or equal to 140, the $keterangan variable is assigned “Genius”.
130-139: If $iq is greater than or equal to 130, the $keterangan variable is assigned “Very Smart (Superior)”.
120-129: If $iq is greater than or equal to 120, the $keterangan variable is assigned “Smart”.
110-119: If $iq is greater than or equal to 110, the $keterangan variable is assigned “Normal Bright”.
90-109: If $iq is greater than or equal to 90, the $keterangan variable is assigned “Average”.
80-89: If $iq is greater than or equal to 80, the $keterangan variable is assigned “Slow”.
70-79: If $iq is greater than or equal to 70, the $keterangan variable is assigned “Moron”.
50-69: If $iq is greater than or equal to 50, the $keterangan variable is assigned “Very Low IQ”.
30-40: If $iq is greater than or equal to 30, the $keterangan variable is assigned “Mental Retardation”.
0-29: If $iq is greater than or equal to 0, the $keterangan variable is assigned “Idiot”.

Invalid Value Handling: If the $iq value does not meet any of the conditions above (e.g., the value is negative or below 0), the program will enter the else block, and the $keterangan variable will be assigned the string “Invalid value”.

Exercise 3

Display the time description based on the current hour.

Morning (Pagi): 05.01 – 11.00
Afternoon (Siang): 11.01 – 15.00
Evening (Sore): 15.01 – 17.00
Night (Malam): 17.01 – 24.00
Early Morning (Dini Hari): 00.01 – 05.00

The following code is the PHP implementation of the problem above:

<?php
$jam = (float) date("H.i");

if ($jam > 17.00 && $jam <= 24.00) {
    $waktu = "Night";
} elseif ($jam > 15.00 && $jam <= 17.00) {
    $waktu = "Evening";
} elseif ($jam > 11.00 && $jam <= 15.00) {
    $waktu = "Afternoon";
} elseif ($jam > 5.00 && $jam <= 11.00) {
    $waktu = "Morning";
} elseif ($jam >= 0.00 && $jam <= 5.00) {
    $waktu = "Early Morning";
} else {
    $waktu = "Invalid time";
}
?>

Program Objective: To determine and display the time division description (such as Morning, Afternoon, Evening) based on the current system time according to the provided time range guidelines.

Input Retrieval: The program retrieves the current system time using the built-in PHP function date("H.i"), which produces a time format of hours and minutes (HH.MM). This time value is then converted into a decimal data type (float) and stored in the $jam variable to facilitate comparison.

Logical Structure (If-Elseif): The program uses a conditional branching structure (with the logical AND operator &&) to map the $jam variable value according to the Exercise 3 guidelines:

Night (Malam): If $jam is greater than 17.00 and less than or equal to 24.00 (representing the 17.01-24.00 range), the $waktu variable is assigned “Night”.
Evening (Sore): If $jam is greater than 15.00 and less than or equal to 17.00 (representing the 15.01-17.00 range), the $waktu variable is assigned “Evening”.
Afternoon (Siang): If $jam is greater than 11.00 and less than or equal to 15.00 (representing the 11.01-15.00 range), the $waktu variable is assigned “Afternoon”.
Morning (Pagi): If $jam is greater than 5.00 and less than or equal to 11.00 (representing the 05.01-11.00 range), the $waktu variable is assigned “Morning”.
Early Morning (Dini Hari): If $jam is greater than or equal to 0.00 and less than or equal to 5.00 (representing the 00.01-05.00 range), the $waktu variable is assigned “Early Morning”.

Invalid Value Handling: If for some reason the $jam value falls outside the 0.00 to 24.00 range, the program will automatically execute the else block, and the $waktu variable will be assigned the string “Invalid time”.

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Learning Basic Logic In PHP

Exercise 1

Exercise 2

Exercise 3