Example 6: Day of the Week
switch-case structure for multiple options
Download file dia_semana🎯 Live Demo
Weekly Calendar
Select a day!
Quick days:
💡 Day facts:
📖 Code Explanation
Complete PHP Code
<?php
$dia = 6;
switch ($dia) {
case 1:
echo t('Lunes');
break;
case 2:
echo t('Martes');
break;
case 3:
echo t('Miércoles');
break;
case 4:
echo t('Jueves');
break;
case 5:
echo t('Viernes');
break;
case 6:
echo t('Sábado');
break;
case 7:
echo t('Domingo');
break;
default:
echo t('No es un día de la semana');
}
?>📝 Line 1: Control variable
$dia = 6;
What does it do? Defines the variable that will control the flow of the switch.
Why is it done this way? Switch needs a variable to compare against the different cases.
💡 Concept: Control variable
En estructuras switch, una sola variable se evalúa múltiples veces contra diferentes valores posibles.
📝 Lines 3-25: switch structure
switch ($dia) { case 1: echo t('Lunes'); break; // ... more cases ... default: echo t('No es un día de la semana');}
What does it do? Evaluates the variable $dia against each case and runs the code for the matching case.
Why is it done this way? Switch is ideal when we have a variable that can take several specific values.
💡 Concept: break
break es crucial en switch. Sin él, PHP ejecutaría todos los casos siguientes (fall-through).
📝 Case default
default: echo t('No es un día de la semana');
What does it do? Runs when no case matches the variable.
Why is it done this way? Handles unexpected values and makes the code more robust.
💡 Concept: Defensive Programming
Siempre incluye un caso default para manejar valores inesperados y prevenir errores.
🔍 Anatomy of the Structure Switch
1. Expression switch
switch ($variable)
The variable that will be evaluated against each case.
2. Cases (cases)
case valor:
Each possible value the variable can have.
3. Code block
// code to execute
The statements that run if there is a match.
4. Break
break;
Ends the execution of the switch.
5. Default
default:
Runs if no case matches.
⚖️ Switch vs If-Else: When to use each one?
✅ Use SWITCH when:
- You compare a variable against specific values
- You have many cases (more than 3-4)
- The conditions are simple equality checks
- The code is more readable with switch
switch ($dia) {
case 1: echo t('Lunes'); break;
case 2: echo t('Martes'); break;
// ...
}✅ Use IF-ELSE when:
- The conditions are complex
- You use operators like >, <, >=
- You have few cases (2-3)
- You need to evaluate multiple variables
if ($edad >= 18) {
echo "Older";
} else {
echo "Younger";
}🚀 Advanced Use Cases for Switch
Multiple cases, same code
Several cases can run the same code.
switch ($dia) {
case 1:
case 2:
case 3:
case 4:
case 5:
echo "Working day";
break;
case 6:
case 7:
echo "Weekend";
break;
}Switch with strings
It also works with text strings.
switch ($color) {
case "red":
echo "Stop";
break;
case "green":
echo "Go";
break;
}Return in switch
You can use return in functions.
function getDia($numero) {
switch ($numero) {
case 1: return t('Lunes');
case 2: return t('Martes');
default: return t('Inválido');
}
}🎯 Key Concepts Learned
structure Switch
- Ideal for multiple options
- More readable than many if-else
- Only compares by equality
- Requires break for each case
Control Flow
- Break ends execution
- Without break: fall-through
- Default handles unexpected cases
- Order of cases can matter
Best Practices
- Always include a default
- Use break in each case
- Keep cases simple
- Document complex cases
💪 Practical Exercise
Extend the days system
Practice these changes to improve your skills:
- switch Convert the if-elseif-else and compare readability
- Add day information in English alongside Spanish
- Create a system that detects whether the day is a workday, weekend or holiday
- Implement a switch that works with day names instead of numbers
- Create a function that receives the day number and returns an array with full information
Solution 1: With if-elseif
<?php
if ($dia == 1) {
echo t('Lunes');
} elseif ($dia == 2) {
echo t('Martes');
} elseif ($dia == 3) {
echo t('Miércoles');
} elseif ($dia == 4) {
echo t('Jueves');
} elseif ($dia == 5) {
echo t('Viernes');
} elseif ($dia == 6) {
echo t('Sábado');
} elseif ($dia == 7) {
echo t('Domingo');
} else {
echo t('No es un día de la semana');
}
?>Solution 2: Bilingual
<?php
switch ($dia) {
case 1:
echo "Lunes / Monday";
break;
case 2:
echo "Martes / Tuesday";
break;
// ... otros días ...
}
?>Solution 3: Day type
<?php
switch ($dia) {
case 1:
case 2:
case 3:
case 4:
case 5:
echo "Día laboral";
break;
case 6:
case 7:
echo "Fin de semana";
break;
default:
echo "Día inválido";
}
?>Solution 4: With strings
<?php
$nombreDia = "lunes"; // en minúsculas
switch ($nombreDia) {
case "lunes":
echo "Día 1";
break;
case "martes":
echo "Día 2";
break;
// ... otros días ...
default:
echo "Día no válido";
}
?>Solution 5: Function with array
<?php
function getDiaInfo($numero) {
switch ($numero) {
case 1:
return ["nombre" => t('Lunes'), "ingles" => "Monday", "tipo" => "laboral"];
case 2:
return ["nombre" => t('Martes'), "ingles" => "Tuesday", "tipo" => "laboral"];
case 6:
return ["nombre" => t('Sábado'), "ingles" => "Saturday", "tipo" => "fin_semana"];
case 7:
return ["nombre" => t('Domingo'), "ingles" => "Sunday", "tipo" => "fin_semana"];
default:
return ["nombre" => "Inválido", "ingles" => "Invalid", "tipo" => "invalido"];
}
}
$info = getDiaInfo(1);
echo $info['nombre']; // Lunes
?>